Method and apparatus of transmitting RLC status report in next generation mobile communication system

ABSTRACT

The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/963,820 filed on Apr. 26, 2018, which is based on and claims priorityunder 35 U.S.C. § 119 to Korean Patent Application No. 10-2017-0053568filed on Apr. 26, 2017 in the Korean Intellectual Property Office, thedisclosures of which are herein incorporated by reference in theirentirety.

BACKGROUND 1. Field

Various embodiments of the present disclosure relate to a method ofreporting an uplink data buffer status to allow a terminal whichtransmits/receives data simultaneously using a plurality of radio accesstechnology (RAT) to transmit the data to a base station in a radiocommunication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’. The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), Full Dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud Radio Access Networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,Coordinated Multi-Points (CoMP), reception-end interference cancellationand the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) andsliding window superposition coding (SWSC) as an advanced codingmodulation (ACM), and filter bank multi carrier (FBMC), non-orthogonalmultiple access (NOMA), and sparse code multiple access (SCMA) as anadvanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

SUMMARY

Accordingly, embodiments of the present disclosure are directed to theprovision of a method of efficiently reporting an uplink data bufferstatus to allow a terminal which transmits/receives data simultaneouslyusing a plurality of radio access technology (RAT) to transmit the datato a base station in a radio communication system.

In addition, in the next generation mobile communication system, whenPDCP layers for each logical channel receive data, data pre-processingcan be performed on the data before receiving an uplink transmission.That is, data processing of the RLC layer and data processing of the MAClayer can also be performed in advance. The reason why the datapre-processing described above can be performed is that there is no dataconcatenation function in the RLC layer. That is, the RLC layerprocesses the data in units of a receiving PDCP PDU (RLC SDU) andtransmits the processed data to the MAC layer. Therefore, in the nextgeneration mobile communication system, the data pre-processing can beperformed for each logical channel, and a plurality of RLC PDUs can begenerated for each logical channel. In the MAC layer, upon receivinguplink transmission resources from the base station, a procedure fordividing the transmission resources for each logical channel isperformed, and the RLC PDUs generated for each logical channel areconfigured as one MAC PDU to perform the transmission.

That is, if one MAC PDU is missed, several RLC PDUs may be missed foreach logical channel. Therefore, there is a need of a method ofefficiently reporting several RLC PDUs missed for each logical channelfrom a receiving end. Accordingly, the present disclosure proposes amethod and apparatus for efficiently reporting an RLC status in a nextgeneration mobile communication system.

Also, since the RLC layer triggers polling according to variousconditions, if data are processed in units of PDCP PDUs, a plurality ofpollings can be transmitted to the receiving end, which may cause aproblem. In addition, there is a need to drive a polling retransmissiontimer (t-pollRetransmit) to prepare the case where the polling is notnormally transmitted to the receiving end. Here, the time to drive thepolling retransmission timer also needs to consider the datapre-processing. In particular, in a multiple access environment to anLTE system and a next generation mobile communication system, theterminal needs to operate the polling retransmission timer differently.

In addition, in order to realize a method of performing channelmeasurement using a synchronization signal newly introduced in the nextgeneration mobile communication system, a method of reporting signalingfor measuring neighboring cells and synchronization signal informationon neighboring cells measured by a terminal to a base station isproposed.

Objects of the present disclosure are not limited to the above-mentionedobjects. That is, other objects that are not mentioned may be obviouslyunderstood by those skilled in the art to which the present disclosurepertains from the following description.

In accordance with an aspect of the present disclosure, a method oftransmitting a radio link control (RLC) status report by a terminal in awireless communication system is provided. The method includesreceiving, from a base station, at least one RLC protocol data unit(PDU), identifying, a missed RLC service data unit (SDU) based on asequence number of the at least one RLC PDU and transmitting, to thebase station, the RLC status report for reporting the missed RLC SDU,and wherein the RLC status report includes a first field for indicatingwhether the RLC SDU is missed.

The RLC status report includes a second field to indicate the sequencenumber of the missed RLC SDU.

An RLC SDU includes a plurality of segments, and the RLC status reportincludes a fifth field to configure a third field and fourth field whichare used to indicate a missed segment.

The third field indicates a start position of the missed segments, andthe fourth field indicates an end position of the missed segments.

The third field is configured to 0, when the start position of themissed segments is equal to a start position of the missed RLC SDUincluding the missed segments.

The fourth field is configured to 0 or 1, when the end position of themissed segments is equal to an end position of the missed RLC SDUincluding the missed segments.

The RLC status report includes a seventh field to configure a sixthfield indicating a range of a consecutively missed RLC SDU, andinformation indicated by the fourth field is varied corresponding to thevalue of the seventh field.

In accordance with an aspect of the present disclosure, a terminal in awireless communication system is provided. The terminal includes atransceiver and a controller coupled with the transceiver and configuredto control the transceiver to receive, from a base station, at least oneRLC protocol data unit (PDU), identify, a missed RLC service data unit(SDU) based on a sequence number of the at least one RLC PDU, andcontrol the transceiver to transmit, to the base station, the RLC statusreport for reporting the missed RLC SDU, and wherein the RLC statusreport includes a first field for indicating whether the RLC SDU ismissed.

The RLC status report includes a second field to indicate the sequencenumber of the missed RLC SDU.

An RLC SDU includes a plurality of segments, and the RLC status reportincludes a fifth field to configure a third field and fourth field whichare used to indicate a missed segment.

The third field indicates a start position of the missed segments, andthe fourth field indicates an end position of the missed segments.

The third field is configured to 0, when the start position of themissed segments is equal to a start position of the missed RLC SDUincluding the missed segments.

The fourth field is configured to 0 or 1, when the end position of themissed segments is equal to an end position of the missed RLC SDUincluding the missed segments.

The RLC status report includes a seventh field to configure a sixthfield indicating a range of a consecutively missed RLC SDU.

According to the embodiment of the present disclosure, even if theplurality of logical channels or the logical channel groups exist, theterminal can elaborately report the buffer status with the smalloverhead.

In addition, according to the present disclosure, it is possible tosmooth the RLC ARQ operation of the RLC layer by proposing the method ofefficiently reporting the ACK/NACK information on the plurality ofmissed RLC PDUs from the receiving end RLC layer to the transmitting endin a RLC layer in the next generation mobile communication system.

In addition, the present disclosure proposes the method of processing,by the receiving end RLC layer, several pollings transmitted by the RLClayer in the next generation mobile communication system, proposes thetime to trigger the polling retransmission timer in consideration of thedata pre-processing at the transmitting end, and proposes the method fordriving, by the terminal, the polling retransmission timer differentlyin the multiple access environment to the LTE system and the nextgeneration mobile communication system.

In addition, according to the present disclosure, it is possible to usethe synchronization signal for the neighboring cell measurement by thedetailed embodiment for the method of receiving, by a terminal, theinformation for measuring synchronization signals of neighboring cellsin the next generation mobile communication system and the method ofreceiving, by a base station, synchronization signal information onneighboring cells when there is no information on neighboring cells.

The effects that may be achieved by the embodiments of the presentdisclosure are not limited to the above-mentioned objects. That is,other effects that are not mentioned may be obviously understood bythose skilled in the art to which the present disclosure pertains fromthe following description.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for certain words and phrases are provided throughout thispatent document. Those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1A is a diagram illustrating a structure of an LTE systemreferenced for the explanation of the present disclosure;

FIG. 1B is a diagram illustrating a radio protocol structure in the LTEsystem referenced for the explanation of the present disclosure;

FIG. 1C is a diagram for explaining a concept of multiple access in LTEand NR;

FIG. 1D is a diagram illustrating an example of a message flow between aterminal and a base station when the present disclosure is applied;

FIGS. 1EA-EH are diagrams of an example of a buffer status report formatproposed in the present disclosure;

FIG. 1F is a diagram illustrating an example of an operation sequence ofthe terminal when the present disclosure is applied;

FIG. 1G is a diagram illustrating an example of a block configuration ofthe terminal according to the embodiment of the present disclosure;

FIG. 2A is a diagram illustrating a structure of an LTE system to whichthe present disclosure may be applied;

FIG. 2B is a diagram illustrating a radio protocol structure in the LTEsystem to which the present disclosure may be applied;

FIG. 2C is a diagram illustrating a structure of a next generationmobile communication system to which the present disclosure may beapplied;

FIG. 2D is a diagram illustrating the radio protocol structure of thenext generation mobile communication system to which the presentdisclosure may be applied;

FIGS. 2EA-2EB are diagrams illustrating a structure of processing datain the LTE system;

FIGS. 2FA-2FB are diagrams illustrating a structure of processing datain the next generation mobile communication system of the presentdisclosure;

FIG. 2G is a diagram illustrating a first method of reporting an RLCstatus according to the present disclosure;

FIGS. 2HA-2HB are diagrams illustrating a second method of reporting anRLC status according to the present disclosure;

FIGS. 2IA-2IC are diagrams illustrating a third method of reporting anRLC status according to the present disclosure;

FIGS. 2JA-2JC are diagrams illustrating a fourth method of reporting anRLC status according to the present disclosure;

FIG. 2K is a diagram illustrating an operation of a terminal to whichthe embodiments of the present disclosure are applied;

FIG. 2L is a diagram illustrating the structure of the terminal to whichthe embodiment of the present disclosure may be applied;

FIG. 2M is a block configuration diagram of TRP in a wirelesscommunication system to which the embodiment of the present disclosuremay be applied;

FIG. 3A is a diagram illustrating a structure of an LTE system to whichthe present disclosure may be applied;

FIG. 3B is a diagram illustrating a radio protocol structure in the LTEsystem to which the present disclosure may be applied;

FIG. 3C is a diagram illustrating a structure of a next generationmobile communication system to which the present disclosure may beapplied;

FIG. 3D is a diagram illustrating the radio protocol structure of thenext generation mobile communication system to which the presentdisclosure may be applied;

FIGS. 3EA-3EB are diagrams illustrating a structure of processing datain the LTE system;

FIGS. 3FA-3FB are diagrams illustrating a structure of processing datain the next generation mobile communication system of the presentdisclosure;

FIG. 3G is a diagram illustrating a scenario in which a terminal isconnected to an LTE system (LTE eNB) and a next generation mobilecommunication system (NR gNB) by a multiple access;

FIG. 3H is a diagram illustrating an operation of a terminal accordingto various embodiments of the present disclosure for a method ofoperating each timer differently in each RLC layer when the terminal isconnected to the LTE system base station and the next generation mobilecommunication system by a multiple access;

FIG. 3I is a diagram illustrating a procedure for establishing aconnection between a base station and a terminal in the presentdisclosure;

FIG. 3J is a diagram illustrating the structure of the terminal to whichthe embodiment of the present disclosure may be applied;

FIG. 3K is a block configuration diagram of the TRP in the wirelesscommunication system to which the embodiment of the present disclosuremay be applied;

FIG. 4A is a diagram illustrating a structure of an LTE systemreferenced for the explanation of the present disclosure;

FIG. 4B is a diagram illustrating the radio protocol structure in theLTE system referenced for the explanation of the present disclosure;

FIG. 4C is a diagram illustrating the structure of the next generationmobile communication system to which the present disclosure is applied;

FIG. 4D is a diagram illustrating a structure of another next generationmobile communication system to which the present disclosure may beapplied.

FIG. 4E is a diagram illustrating a structure of a subframe in which asynchronization signal is transmitted in the next generation mobilecommunication system;

FIG. 4F is a diagram for explaining an overall operation of a channelmeasurement using the synchronization signal proposed in the presentdisclosure;

FIGS. 4GA-4GB are diagrams for explaining a channel measurement andreporting operation using the synchronization signal of the terminal towhich the present disclosure is applied;

FIGS. 4HA-4HB are diagrams diagram for explaining a channel measurementsetting and applying operation using the synchronization signal of thebase station to which the present disclosure is applied;

FIG. 4I is a block diagram illustrating an internal structure of theterminal to which the present disclosure is applied;

FIG. 4J is a block diagram illustrating a configuration of the basestation according to the present disclosure;

FIG. 5A is a diagram illustrating a structure of the next generationmobile communication system;

FIG. 5B is a diagram for explaining a case in which an access connectionconfiguration information is urgently renewed in the existing LTEsystem;

FIG. 5C is a diagram for explaining a method for renewing accessconnection configuration information in the next generation mobilecommunication system according to the present disclosure;

FIG. 5D is a flowchart of the terminal operation in the presentdisclosure;

FIG. 5E is a diagram for explaining a first method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure;

FIG. 5F is a diagram for explaining a second method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure;

FIG. 5G is a diagram for explaining a third method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure;

FIG. 5H is a diagram for explaining a fourth method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure;

FIG. 5I is a block diagram illustrating an internal structure of theterminal to which the present disclosure is applied; and

FIG. 5J is a block diagram illustrating a configuration of the basestation according to the present disclosure.

DETAILED DESCRIPTION

FIGS. 1A through 5J, discussed below, and the various embodiments usedto describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

Hereinafter, an operation principle of the present disclosure will bedescribed in detail with reference to the accompanying drawings.Hereinafter, when it is determined that the detailed description of theknown art related to the present disclosure may obscure the gist of thepresent disclosure, the detailed description thereof will be omitted.Further, the following terminologies are defined in consideration of thefunctions in the present disclosure and may be construed in differentways by the intention or practice of users and operators. Therefore, thedefinitions thereof should be construed based on the contents throughoutthe specification.

Terms identifying an access node, terms indicating network entity, termsindicating messages, terms indicating an interface between networkentities, terms indicating various types of identification information,and so on that are used in the following description are exemplified forconvenience of explanation. Accordingly, the present disclosure is notlimited to terms to be described below and other terms indicatingobjects having the equivalent technical meaning may be used.

Hereafter, for convenience of explanation, the present disclosure usesterms and names defined in the 3rd generation partnership project longterm evolution (3GPP LTE) that is the latest standard among thecurrently communication standards. However, the present disclosure isnot limited to the terms and names but may also be identically appliedeven to the system according to other standards. In particular, thepresent disclosure may be applied to 3GPP new radio (NR: 5G mobilecommunication standard).

FIG. 1A is a diagram illustrating a structure of an LTE systemreferenced for the explanation of the present disclosure.

Referring to FIG. 1A, a wireless communication system is configured toinclude a plurality of base stations 1 a-05, 1 a-10, 1 a-15, and 1 a-20,a mobility management entity (MME) 1 a-25, a serving-gateway (S-GW) 1a-30. A user equipment (hereinafter, UE or terminal) 1 a-35 accesses anexternal network through the base stations 1 a-05, 1 a-10, 1 a-15, and 1a-20 and the S-GW 1 a-30.

The base stations 1 a-05, 1 a-10, 1 a-15, and 1 a-20 are access nodes ofa cellular network and provide a radio access to terminals that accessesa network. That is, in order to serve traffic of users, the basestations 1 a-05, 1 a-10, 1 a-15, and 1 a-20 collect and schedule statusinformation such as a buffer status, an available transmission powerstatus, a channel status, or the like of the terminals, therebysupporting a connection between the terminals and a core network (CN).The MME 1 a-25 is an apparatus for performing various control functionsas well as a mobility management function for the terminal and isconnected to a plurality of base stations, and the S-GW 1 a-30 is anapparatus for providing a data bearer. Further, the MME 1 a-25 and theS-GW 1 a-30 may further perform authentication, bearer management, andthe like on the terminal accessing the network and may process packetsthat are to be received from the base stations 1 a-05, 1 a-10, 1 a-15,and 1 a-20 and packets that are to be transmitted to the base stations 1a-05, 1 a-10, 1 a-15, and 1 a-20.

FIG. 1B is a diagram illustrating a radio protocol structure in the LTEsystem referenced for the explanation of the present disclosure. The NRto be defined below may be partially different from the radio protocolstructure in the present figure, but will be described for convenienceof explanation of the present disclosure.

Referring to FIG. 1B, the radio protocol of the LTE system consists ofpacket data convergence protocols (PDCPs) 1 b-05 and 1 b-40, radio linkcontrols (RLCs) 1 b-10 and 1 b-35, and medium access controls (MACs) 1b-15 and 1 b-30 in the terminal and the ENB, respectively. The packetdata convergence protocols (PDCPs) 1 b-05 and 1 b-40 performs operationssuch as compression/recovery of an IP header, and the radio linkcontrols (hereinafter, referred to as RLC) 1 b-10 and 1 b-35 reconfigurea PDCP packet data unit (PDU) to be an appropriate size. The MACs 1 b-15and 1 b-30 are connected to several RLC layer apparatuses configured inone terminal and perform an operation of multiplexing RLC PDUs into aMAC PDU and demultiplexing the RLC PDUs from the MAC PDU. Physicallayers 1 b-20 and 1 b-25 perform an operation of channel-coding andmodulating an upper layer data, making the upper layer data into an OFDMsymbol and transmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to theupper layer. Further, the physical layer uses an HARQ (Hybrid ARQ) foradditional error correction and a receiving end transmits whether toreceive the packet transmitted from a transmitting end in 1 bit. This iscalled HARQ ACK/NACK information. The downlink HARQ ACK/NACK informationon the uplink transmission may be transmitted on a physical hybrid-ARQindicator channel (PHICH) physical channel, and the uplink HARQ ACK/NACKinformation on the downlink transmission may be transmitted on aphysical uplink control channel (PUCCH) or physical uplink sharedchannel (PUSCH) physical channel.

Meanwhile, the PHY layer may consist of one or a plurality offrequency/carriers, and a technology of simultaneously setting and usinga plurality of frequencies in one base station is called carrieraggregation (hereinafter, referred to as CA). Unlike using only onecarrier for communication between the terminal (or user terminal (UE))and the base station (E-UTRAN NodeB, eNB), the CA technologyadditionally uses a main carrier and one or a plurality of sub-carriersto be able to surprisingly increase throughput as many as the number ofsub-carriers. Meanwhile, in the LTE, a cell within the base stationusing the main carrier is called a primary cell (PCell) and thesub-carrier is called a secondary cell (SCell). The technology forextending the CA function to two base stations is referred to as dualconnectivity (hereinafter, referred to as DC). In the DC technology, theterminal simultaneously connects and uses a master base station (MasterE-UTRAN Node B (MeNB) or Master Node B (MN)) and a secondary basestation (Secondary E-UTRAN Node B (SeNB) or Secondary NodeB (SN)), andcells belonging to the master base station are referred to as a mastercell group (hereinafter, referred to as MCG) and cells belonging to thesecondary base station are called a secondary cell group (hereinafter,referred to as SCG). There are representative cells for each cell group.The representative cell for the master cell group is a primary cell(hereinafter, referred to as PCell), and the representative cell for thesecondary cell group is referred to as a primary secondary cell(hereinafter, referred to as PSCell). When the above-mentioned NR isused, the MCG uses the LTE technology, and the SCG uses the NR, suchthat the terminal may simultaneously use the LTE and the NR.

Although not illustrated in the present drawings, radio resource control(hereinafter, referred to as RRC) layers exist at a higher part of thePDCP layer of the terminal and the base station, and the RRC layer mayreceive/transmit access and various configuration control messages for aradio resource control. For example, the terminal may be instructed tomeasure the neighboring cells using the RRC layer message, and theterminal may report the measured results to the base station using theRRC layer message.

FIG. 1C is a diagram illustrating the concept of the dual connectivity.

Using the dual connectivity technology, the terminal may simultaneouslyconnect and use two base stations. In the illustrated example, it isillustrated that the terminal 1 c-05 simultaneously connects a macrobase station 1 c-00 using the LTE technology and a small cell basestation 1 c-10 using the NR technology to transmit/receive data. Themacro base station is referred to as Master E-UTRAN NodeB (MeNB), andthe small cell base station is referred to as Secondary E-UTRAN NodeB(SeNB). A plurality of small cells may be present in a service area ofthe MeNB, and the MeNB is connected to the SeNBs via a wired backhaulnetwork 1 c-15. A set of serving cells received from the MeNB isreferred to as a master cell group (MCG) 1 c-20. In the MCG, one servingcell is a primary cell (PCell) 1 c-25 which necessarily has allfunctions such as connection establishment, connection re-establishment,and handover that have been performed by the existing cells. Also, thePCell may include a physical uplink control channel (PUCCH) which is anuplink control channel. The serving cell other than the PCell is calleda secondary cell (SCell) 1 c-30. FIG. 1C illustrates a scenario in whichthe MeNB provides one SCell and the SeNB provides three SCell. The setof serving cells provided by the SeNB is called the secondary cell group(SCG) 1 c-40. When the terminal transmits/receives data from two basestations, the MeNB issues, to the SeNB, a command to add, change, orremove serving cells provided by the SeNB. In order to issue such acommand, the MeNB may configure the terminal to measure the serving celland neighboring cells. The terminal should report the measured resultsto the MeNB based on the configuration information. In order for theSeNB to efficiently transmit/receive data to the terminal, the servingcell which plays a role similar to the PCell of the MCG is used. In thepresent disclosure, this is referred to as a primary SCell (PSCell). ThePSCell is defined as one of the serving cells of the SCG, and mayinclude the PUCCH which is the uplink control channel. The PUCCH is usedto allow the terminal to transmit HARQ ACK/NACK information, channelstatus information (CSI), scheduling request (SR) and the like to thebase station.

FIG. 1D is a diagram illustrating message flow between the terminal andthe base station when using a method of reporting a data buffer statusfor an uplink data transmission proposed in the present disclosure.

In the present drawing, the terminal 1 d-01 in an idle mode (RRC_IDLE)performs an access to the LTE cell for reasons such as a generation ofdata to be transmitted (1 d-11). In the idle mode, data may not betransmitted because the terminal is not connected to the network forpower saving or the like, and a transition to a connection mode(RRC_CONNECTED) is used to transmit data. If the terminal succeeds inthe access procedure to the LTE cell 1 d-03, the terminal changes itsstate to the connection mode (RRC_CONNECTED).

Thereafter, the base station creates a logical (or virtual) channel onwhich data may be transmitted so that the terminal may transmit data. Alogical (or virtual) channel on which data may be transmitted is calleda data radio bearer (DRB). In contrast, a logical (or virtual) channelon which a control signal may be transmitted is called a signaling radiobearer (DRB). The DRB and the SRB each have a logical channel identity(LCID). When the signaling or data is transmitted on the downlink or theuplink, the DRB and the SRB transmit the corresponding logical channelidentifier by including the logical channel identifier in a headeraccording to the corresponding data type in the MAC layer, so that thereceiving end identifies whether the corresponding packet is signalingor data. If the corresponding data is the data, the receiving enddetermines which DRB the data belong to identify the received data.

In order to configure the DRB as described above, the base stationtransmits an RRCConnectionReconfiguration message to the terminal tonewly configure the DRB to the terminal, in which the DRB configurationinformation includes the above-mentioned PDCP, RLC and MAC layer relatedconfiguration information (1 d-13). If the plurality of DRBs areconfigured, separate configuration information is included for each DRB.In addition, it is possible to configure logical channel group (LCG)information for each DRB as the MAC layer related information. Forexample, if the base station configures a total of 5 DRBs for the UE,the LCIDs each may be allocated to each of the DRBs as 3, 4, 5, 6, and7. As will be described later, the LCG is used when the terminalrequests a resource to the base station. For example, if the terminalhas 100 bytes of data to be transmitted in LCID No. 3, 100 bytes of datato be transmitted in LCID No. 4, and 100 bytes of data to be transmittedin LCID No. 7, the terminal may report the base station that there are200 bytes of data to be transmitted in LCG No. 1 and 100 bytes of datato be transmitted in LCG No. 3, instead of reporting the amount of datato be transmitted in each LCID.

The terminal receiving the configuration information may transmit to thebase station an acknowledgement message indicating that theconfiguration information has been successfully received. For example,the terminal may transmit the acknowledgment message to the base stationusing an RRConnectionReconfigurationComplete message of the RRC layer.

Thereafter, if the terminal has data to be transmitted by DRB to thebase station as described above, the terminal reports the amount of datato be transmitted for each LCG according to a first buffer status report(BSR) format (1 d-17). The BSR is divided as follows according to thecondition in which the transmission is triggered.

-   -   First type: Regular BSR        -   The BSR transmitted when the terminal has data that can be            transmitted for the SRB/DRB belonging to the LCG, and a BSR            retransmission timer (retxBSR-Timer) expires.        -   BSR transmitted when the data to be transmitted from the            upper layer (RLC or PDCP layer) for the SRB/DRB belonging to            the LCG described above are generated and the data have            priority higher than the logical channel/wireless bearer            belonging to any LCG.        -   BSR transmitted when the data to be transmitted from the            upper layer (RLC or PDCP layer) for the logical            channel/radio bearer belonging to the LCG are generated and            no data exists in any data except the data.    -   Second type: Periodic BSR        -   BSR transmitted when a periodic BSR-timer            (periodicBSR-Timer) configured in the terminal expires.    -   Third type: Padding BSR        -   BSR transmitted when the uplink resource is allocated and            the padding bit filling the space remaining after the data            are transmitted is equal to or larger than the sum of the            size of the BSR MAC control element (CE) and the side of the            sub-header of the BSR MAC CE.        -   If the packets exist in the plurality of LCG buffers, the            truncated BSR is transmitted.

Accordingly, if padding (i.e., remaining space) occurs upon receivingthe uplink resource allocation from the base station, it is possible totransmit a long BSR or a short BSR/truncated BSR depending on the sizeof the remaining space. The first buffer status report format will bedescribed in detail in FIGS. 1EA-EH. The base station receiving thereport allocates the uplink resource to the terminal (1 d-19). Theterminal receiving the resource allocation information transmits data inthe buffer as the corresponding resource to the base station (1 d-21).

Meanwhile, when the terminal supports the DC and the NR cell existsaround the terminal according to the neighbor cell measurement reportinformation received from the terminal, the base station transmits theSCG information to the terminal in order to set the DC function (1d-23). The information may be transmitted through theRRCConnectionReconfiguration message, and the SCG configurationinformation may include addition and revocation information for thePSCells and SCells added to the SCG. In addition, if the DC is set forthe DRB as described above, the following bearer types exist.

-   -   MCG bearer: Bearer transmitted only to the MCG    -   MCG split bearer: in the case of the downlink from the core        network connected to the MCG, bearer on which data is        transmitted by being divided into the MCG and the SCG; in the        case of the uplink, bearer on which data may be transmitted by        being divided into the MCG and the SCG and the packet received        by the SCG is transmitted to the MCG to be transmitted to the        MCG side core network.    -   SCG bearer: Bearer transmitted only to the SCG    -   SCG split bearer: In the case of the downlink from the core        network connected to the SCG, bearer on which data is        transmitted by being divided into the SCG and the MCG; in the        case of the uplink, bearer on which data may be transmitted by        being divided into the MCG and the SCG and the packet received        by the MCG is transmitted to the SCG to be transmitted to the        SCG side core network.

If the bearer type of the DRB is the MCG split bearer, the SCG bearer,or the SCG split bearer, the LCID and LCG information used in the SCGmay be additionally transmitted to the configuration information. Atthis time, the LCID and LCG information to be used in the SCG includedin the configuration information are independent of the LCID and LCGinformation used in the MCG. For example, the LCID used for the DRB inthe LTE has values from 3 to 10, but the LCID used for the DRB in the NRmay have other ranges such as 4 to 15. In addition, the LCG also hasvalues from 0 to 3 in the LTE, but can have values from 0 to 7 in theNR.

Thereafter, the terminal transmits a message confirming that it receivesthe configuration information, which may be transmitted using theRRCConnectionReconfigurationComplete message (1 d-25). Accordingly, theterminal can simultaneously transmit and receive data using the LTE cell1 d-03 which is the MCG, and the NR cell 1 d-05 which is the SCG.

Thereafter, if the terminal wants to transmit data to the SCG for theDRB configured to be transmitted to the SCG, the terminal reports theamount of data to be transmitted to each LCG according to the secondbuffer status report format (1 d-27). The second buffer status reportformat will be described in detail in FIGS. 1EA-EH. The base stationreceiving the report allocates the uplink resource to the terminal (1d-29). The terminal receiving the resource allocation informationtransmits data in the buffer as the corresponding resource to the basestation (1 d-31).

FIGS. 1Ea to 1Eh are diagrams illustrating an example of a buffer statusreport format proposed in the present disclosure.

FIGS. 1Ea and 1Eb are examples of a first buffer status report format.

FIG. 1Ea illustrates a short BSR MAC control element (MAC CE: controlmessage used in the MAC layer) format that transmits the buffer statusreport for one LCG. In the LTE, there are a maximum of four LCGs, sofour LCGs (i.e., 00, 01, 10, and 11) are represented by two bits, andthe buffer status step thereof is represented in 64 steps (2{circumflexover ( )} 6) by six bits. As an example of 64 steps, a range as shown inTable 6.1.3.1 of the 3GPP standard TS 36.321 may be used.

FIG. 1Eb illustrates a long BSR MAC CE format which transmits a bufferstatus report for all four LCGs. That is, the buffer status for fourLCGs of the LTE, respectively, is transmitted. Buffer Size #0 is mappedto a buffer status of LCG No. 0, and Buffer Size #1 is mapped to abuffer status of LCG No. 1.

If padding is generated due to a margin in the allocated uplinkresources as described above, the padding BSR may be transmitted. Forexample, when the padding is generated enough to transmit the long BSRMAC CE, the long BSR MAC CE is transmitted. On the other hand, if thelong BSR MAC CE may not be transmitted, but only the size capable oftransmitting the short BSR MAC CE remains and data exists in only oneLCG, the short BSR MAC CE is transmitted. If the Long BSR MAC CE may notbe transmitted, but only a size enough to transmit the Short BSR MAC CEremains and data exists in a plurality of LCGs, data is transmitted inthe same format as the Short BSR MAC CE, but the corresponding MAC CEuses different logical channel identifiers to inform the base stationthat the corresponding MAC CE is the truncated BSR MAC CE, therebyinforming the base station that there is data in another LCG notincluded in the LCG ID of FIG. 1Ea.

FIGS. 1Ec, 1Ed, 1Ee, 1Ef, 1Eg, and 1Eh are examples of the second bufferstatus report format used in the NR. The NR assumed the situation wherethe number of LCGs are increasing (e.g., from 4 to 8 or 16 in theexisting LTE), or may report the buffer status for each LCID instead ofusing the LCG. If 8 or fewer LCGs or LCIDs are used, the format of 1Ecor 1Ee or 1Eg may be used as the second buffer status report format, andif more than 9 LCGs or LCIDs are used, the format of 1Ed or 1Ef or 1Ehcan be used as the second buffer status report format.

In FIGS. 1Ec, 1Eg, and 1Eg, 8 bits of a first byte may each indicate theLCG or the LCID. (That is, bit map). In the case of the LCG, each bitmay mean Nos. 0 to 7, and in the case of the LCG, each bit may mean Nos.1 to 8. In addition, 16 bits of the first and second bytes in FIGS. 1Ed,1Ef, and 1Eh may each indicate the LCG or the LCID (i.e., bitmap). Forexample, in the case of the LCG, each bit may mean Nos. 1 to 16 and inthe case of the LCID, each bit may mean Nos. 1 TO 16. Buffer sizeinformation corresponding to the corresponding LCG or LCID may beincluded in the buffer status report according to the bit information ofthe bitmap. For example, if the corresponding bit is set to be 1, thebuffer size information corresponding to the corresponding LCG or LCIDis included. For example, in the case of FIG. 1Ec, when the LCG is usedand data exists in the buffer in the LCG ID #1, #5, and #6, data isincluded in the bit map as 01000110, and the buffer sizes correspondingto 1 in the bitmap are each included. In this drawing, on the assumptionthat that each buffer size has a length of 1 byte, it was assumed that abuffer status report having a total of 4 bytes obtained by summing 1byte of the bitmap and 1*3=3 bytes which are the product of the numberof 1s of the bitmap by each buffer size is generated. As describedabove, if the buffer size is a size of 1 byte, that is, a size of 8bits, the buffer status of 2{circumflex over ( )}8=256 steps may bereported, and the alignment even in units of byte may be made asillustrated in this drawing.

On the other hand, the buffer status report format shown in FIGS. 1Ee,1Ef, 1Eg, and 1Eh includes discard indicator information together withbuffer size fields having a length of 7 bits for each LCG or LCID. Ifthe field is set to be 1, the buffer of the corresponding LCG or LCIDshould be transmitted quickly, and if the discard indicator is nottransmitted within x milliseconds, the terminal informs the base stationthat the packet is deleted. The x value may be a value that the terminalinforms to the base station in advance or a value set by the basestation. For example, when the base station sets the DRB, the x valuemay be set. That is, if the packet of the terminal is useless data afterx milliseconds (for example, if a too large delay occurs in the case ofvoice, the packet becomes meaningless) to be deleted, the base stationcan set the terminal to use the discard indicator. In addition, in FIGS.1Eg and 1Eh, if the discard indicator information is set to be ‘1’,buffer size #Y to be discarded soon may be additionally informed alongwith the discard indicator. Accordingly, the base station quicklyallocates uplink resources to the data received by the discard indicatortogether with the buffer status report, thereby preventing the loss ofthe packet.

FIG. 1F is an operation flow chart illustrating the terminal to whichthe present disclosure is applied.

In FIG. 1F, the terminal completes the connection procedure to the basestation and is in a connected state (RRC_CONNECTED). Accordingly, it isassumed that the base station transmits the RRCConnectionReconfigurationmessage to the terminal to set the DRB for data transmission to theterminal (1 f-01). Accordingly, the LCG and the like may be set for eachDRB.

Thereafter, if the terminal supports the dual connectivity (DC) and theNR cell exists around the terminal according to the neighboring cellmeasurement report information received from the terminal, the terminalreceives the SCG configuration in which the NRG cell searched by thebase station is added to the SCG (1 f-03). The configuration informationmay include the addition and revocation information for the PSCell andthe SCell added to the SCG as described above with reference to FIG. 1D,and the LCID and LCG information to be used in the NR may beadditionally transmitted.

Thereafter, if the uplink data belonging to the corresponding databearer is generated in the terminal (1 f-05), the terminal can decide totransmit the uplink data to the LTE or the NR depending on the set valueof the base station. Examples of the set value may include a basictransmission direction and a predetermined threshold value that the basestation provides to the terminal. If the amount of uplink data is equalto or less than (or less than) the predetermined threshold value, theuplink data may be transmitted to the established basic transmissiondirection (e.g., NR or LTE), and if the amount of uplink data is above(or equal to or more than) the predetermined threshold, the uplink datamay be transmitted in both of the LTE and NR directions. The basictransmission direction can be transmitted by DRB or in units ofterminal. Although not shown in the present disclosure, for the DRBexpected that the delay is short or the amount of data is large, thebase station establishes the NR for the terminal as the basictransmission direction. Alternatively, if it is determined that theamount of traffic is large according to the buffer status reportinformation reported from the terminal even if the basic transmissiondirection is the LTE, the base station may re-establish the basictransmission direction as NR.

Meanwhile, the terminal may receive the uplink resource allocationinformation from the base station, and if the resource previouslyallocated for the uplink data transmission remains, as described above,the terminal may transmit the buffer status report instead of thepadding. Accordingly, if there is a resource remaining after theterminal receives the uplink resource allocation information from thebase station through the LTE while having data to be transmitted throughthe LTE, the terminal may use the above-mentioned first buffer statusreport to the padding buffer status report. If there is no remainingresource, the terminal may receive the uplink allocation by transmittinga scheduling request previously configured by the base station orreceive the uplink allocation by performing the random access, therebytransmitting a Regular BSR (1 f-11). Thereafter, the terminal maytransmit the uplink data stored in the buffer according to the uplinkresource allocation information received from the base station (1 f-13).

If there is a resource remaining after the terminal receives the uplinkresource allocation information from the base station through the NRwhile having data to be transmitted through the NR, the terminal maytransmit the padding buffer status report using the second buffer statusreport described above. If there is no remaining resource, the terminalmay receive the uplink allocation by transmitting the scheduling requestpreviously set by the base station or receive the uplink allocation byperforming the random access, thereby transmitting the Regular BSR (1f-21). Thereafter, the terminal may transmit the uplink data stored inthe buffer according to the uplink resource allocation informationreceived from the base station (1 f-23).

FIG. 1G illustrates a block configuration of the terminal according tothe embodiment of the present disclosure.

Referring to FIG. 1G, the terminal includes a radio frequency (RF)processor 1 g-10, a baseband processor 1 g-20, a memory 1 g-30, and acontroller 1 g-40.

The RF processor 1 g-10 serves to transmit/receive a signal through aradio channel, such as band conversion and amplification of a signal.That is, the RF processor 1 g-10 up-converts a baseband signal providedfrom the baseband processor 1 g-20 into an RF band signal and thentransmits the baseband signal through an antenna and down-converts theRF band signal received through the antenna into the baseband signal.For example, the RF processor 1 g-10 may include a transmitting filter,a receiving filter, an amplifier, a mixer, an oscillator, a digital toanalog converter (DAC), an analog to digital converter (ADC), or thelike. FIG. 1G illustrates only one antenna but the terminal may includea plurality of antennas. Further, the RF processor 1 g-10 may includethe plurality of RF chains. Further, the RF processor 1 g-10 may performbeamforming. For the beamforming, the RF processor 1 g-10 may adjust aphase and a size of each of the signals transmitted and received througha plurality of antennas or antenna elements.

The baseband processor 1 g-20 performs a conversion function between thebaseband signal and the bit string according to a physical layerstandard of the system. For example, when data are transmitted, thebaseband processor 1 g-20 generates complex symbols by coding andmodulating a transmitting bit string. Further, when data are received,the baseband processor 1 g-20 recovers the received bit string bydemodulating and decoding the baseband signal provided from the RFprocessor 1 g-10. For example, according to the orthogonal frequencydivision multiplexing (OFDM) scheme, when data are transmitted, thebaseband processor 1 g-20 generates the complex symbols by coding andmodulating the transmitting bit string, maps the complex symbols tosub-carriers, and then performs an inverse fast Fourier transform (IFFT)operation and a cyclic prefix (CP) insertion to configure the OFDMsymbols. Further, when data are received, the baseband processor 1 g-20divides the baseband signal provided from the RF processor 1 g-10 in anOFDM symbol unit and recovers the signals mapped to the sub-carriers bya fast Fourier transform (FFT) operation and then recovers the receivingbit string by the modulation and decoding.

The baseband processor 1 g-20 and the RF processor 1 g-10 transmit andreceive a signal as described above. Therefore, the baseband processor 1g-20 and the RF processor 1 g-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. Further, at least oneof the baseband processor 1 g-20 and the RF processor 1 g-10 may includedifferent communication modules to process signals in differentfrequency bands. Further, different frequency bands may include a superhigh frequency (SHF) (for example: 2.5 GHz, 5 GHz) band, a millimeterwave (for example: 60 GHz) band.

The memory 1 g-30 stores data such as basic programs, applicationprograms, and configuration information or the like for the operation ofthe terminal.

The controller 1 g-40 controls the overall operations of the terminal.For example, the controller 1 g-40 transmits/receives a signal throughthe baseband processor 1 g-20 and the RF processor 1 g-10. Further, thecontroller 1 g-40 records and reads data in and from the memory 1 g-30.For this purpose, the controller 1 g-40 may include at least oneprocessor. For example, the controller 1 g-40 may include acommunication processor (CP) performing a control for communication andan application processor (AP) controlling an upper layer such as theapplication programs. According to the embodiment of the presentdisclosure, the controller 1 g-40 includes a multi-link processor 1 g-42that performs the processing to be operated in a multi-link mode. Forexample, the controller 1 g-40 may control the terminal to perform theprocedure illustrated in the operation of the terminal illustrated inFIG. 1F.

According to the embodiment of the present disclosure, the terminalreceives the SCG addition and the specific configuration for each DRB,so that the terminal determines which base station data transmits to andgenerates the format suitable for the corresponding base station toreport the buffer status of the terminal.

The methods according to the embodiments described in claims orspecification of the present disclosure may be implemented in hardware,software, or a combination of hardware and software.

When the methods are implemented in the software, a computer readablestorage medium storing at least one program (software module) may beprovided. At least one programs stored in the computer readable storagemedium is configured for execution by at least one processor within anelectronic device. At least one program includes instructions that allowthe electronic device to execute the methods according to theembodiments described in the claims or specification of the presentdisclosure.

The program (software module, software) may be stored in a random accessmemory, a non-volatile memory including a flash memory, a read onlymemory (ROM), an electrically erasable programmable read only memory(EEPROM), a magnetic disc storage device, a compact disc-ROM (CD-ROM),digital versatile discs (DVDs) or other types of optical storagedevices, and a magnetic cassette. Alternatively, the programs may bestored in the memory that is configured of combinations of some or allof the memories. Further, each configuration memory may also be includedin plural.

Further, the program may be stored in an attachable storage device thatmay be accessed through communication networks such as Internet, anintranet, a local area network (LAN), a wide LAN (WLAN), and a storagearea network (SAN) or a communication network configured in acombination thereof. The storage device may access a device performingthe embodiment of the present disclosure through an external port.Further, a separate storage device on the communication network may alsoaccess a device performing the embodiment of the present disclosure.

In the detailed embodiments of the present disclosure, componentsincluded in the present disclosure are represented by a singular numberor a plural number according to the detailed embodiment as describedabove. However, the expressions of the singular number or the pluralnumber are selected to meet the situations proposed for convenience ofexplanation and the present disclosure is not limited to the singlecomponent or the plural components and even though the components arerepresented in plural, the component may be configured in a singularnumber or even though the components are represented in a singularnumber, the component may be configured in plural.

Although embodiments of the present disclosure have been disclosed forillustrative purposes, various modifications, additions andsubstitutions are possible, without departing from the scope and spiritof the disclosure as disclosed in the accompanying claims. Accordingly,the scope of the present disclosure is not construed as being limited tothe described embodiments but is defined by the appended claims as wellas equivalents thereto.

FIG. 2A is a diagram illustrating a structure of an LTE system to whichthe present disclosure may be applied.

As illustrated in FIG. 1A, a radio access network of an LTE system isconfigured to include next generation base stations (evolved node B,hereinafter, ENB, Node B, or base station) 2 a-05, 2 a-10, 2 a-15, and 2a-20, a mobility management entity (MME) 2 a-25, and a serving-gateway(S-GW) 2 a-30. User equipment (hereinafter, UE or terminal) 2 a-35accesses an external network through the ENBs 2 a-05 to 2 a-20 and theS-GW 2 a-30.

In FIG. 2A, the ENBs 2 a-05 to 2 a-20 correspond to the existing node Bof the UMTS system. The ENB is connected to the UE 2 a-35 through aradio channel and performs more complicated role than the existing nodeB. In the LTE system, in addition to a real-time service like a voiceover Internet protocol (VoIP) through the Internet protocol, all theuser traffics are served through a shared channel and therefore anapparatus for collecting and scheduling status information such as abuffer status, an available transmission power status, and a channelstatus of the terminals is used. Here, the eNBs 2 a-05 to 2 a-20 takecharge of the collecting and scheduling. One ENB generally controls aplurality of cells. For example, to implement a transmission rate of 100Mbps, the LTE system uses, as a radio access technology, orthogonalfrequency division multiplexing (hereinafter, OFDM) in, for example, abandwidth of 20 MHz. Further, an adaptive modulation & coding(hereinafter, referred to as AMC) determining a modulation scheme and achannel coding rate according to a channel status of the terminal isapplied. The S-GW 2 a-30 is an apparatus for providing a data bearer andgenerates or removes the data bearer according to the control of the MME2 a-25. The MME is an apparatus for performing a mobility managementfunction for the terminal and various control functions and is connectedto a plurality of base stations.

FIG. 2B is a diagram illustrating a radio protocol structure in the LTEsystem to which the present disclosure may be applied.

Referring to FIG. 2B, the radio protocol of the LTE system is configuredto include packet data convergence protocols (PDCPs) 2 b-05 and 2 b-40,radio link controls (RLCs) 2 b-10 and 2 b-35, and medium access controls(MACs) 2 b-15 and 2 b-30, respectively, in the terminal and the ENB,respectively. The packet data convergence protocols (PDCPs) 2 b-05 and 2b-40 are in charge of operations such as IP headercompression/decompression. The main functions of the PDCP are summarizedas follows.

-   -   Header compression and decompression function (Header        compression and decompression: ROHC only)    -   Transfer function of user data (Transfer of user data)    -   In-sequence delivery function (In-sequence delivery of upper        layer PDUs at PDCP re-establishment procedure for RLC AM)    -   Reordering function (For split bearers in DC (only support for        RLC AM): PDCP PDU routing for transmission and PDCP PDU        reordering for reception)    -   Duplicate detection function (Duplicate detection of lower layer        SDUs at PDCP re-establishment procedure for RLC AM)    -   Retransmission function (Retransmission of PDCP SDUs at handover        and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery        procedure, for RLC AM)    -   Ciphering and deciphering function (Ciphering and deciphering)    -   Timer-based SDU discard function (Timer-based SDU discard in        uplink)

The radio link controls (hereinafter, referred to as RLCs) 2 b-10 and 2b-35 reconfigures the PDCP packet data unit (PDU) to an appropriate sizeto perform the ARQ operation or the like. The main functions of the RLCare summarized as follows.

-   -   Data transfer function (Transfer of upper layer PDUs)    -   ARQ function (Error Correction through ARQ (only for AM data        transfer))    -   Concatenation, segmentation, reassembly functions        (Concatenation, segmentation and reassembly of RLC SDUs (only        for UM and AM data transfer))    -   Re-segmentation function (Re-segmentation of RLC data PDUs (only        for AM data transfer))    -   Reordering function (Reordering of RLC data PDUs (only for UM        and AM data transfer)    -   Duplicate detection function (Duplicate detection (only for UM        and AM data transfer))    -   Error detection function (Protocol error detection (only for AM        data transfer))    -   RLC SDU discard function (RLC SDU discard (only for UM and AM        data transfer))    -   RLC re-establishment function (RLC re-establishment)

The MACs 2 b-15 and 2 b-30 are connected to several RLC layerapparatuses configured in one terminal and perform an operation ofmultiplexing RLC PDUs into a MAC PDU and demultiplexing the RLC PDUsfrom the MAC PDU. The main functions of the MAC are summarized asfollows.

-   -   Mapping function (Mapping between logical channels and transport        channels)    -   Multiplexing/demultiplexing function        (Multiplexing/demultiplexing of MAC SDUs belonging to one or        different logical channels into/from transport blocks (TB)        delivered to/from the physical layer on transport channels)    -   Scheduling information reporting function (Scheduling        information reporting)    -   HARQ function (Error correction through HARQ)    -   Priority handling function between logical channels (Priority        handling between logical channels of one UE)    -   Priority handling function between terminals (Priority handling        between UEs by means of dynamic scheduling)    -   MBMS service identification function (MBMS service        identification)    -   Transport format selection function (Transport format selection)    -   Padding function (Padding)

Physical layers 2 b-20 and 2 b-25 perform an operation of channel-codingand modulating an upper layer data, making the upper layer data as anOFDM symbol and transmitting them to a radio channel, or demodulatingand channel-decoding the OFDM symbol received through the radio channeland transmitting the demodulated and channel-decoded OFDM symbol to theupper layer.

FIG. 2C is a diagram illustrating a structure of a next generationmobile communication system to which the present disclosure may beapplied.

Referring to FIG. 2C, a radio access network of a next generation mobilecommunication system (hereinafter referred to as NR or 5G) is configuredto include a next generation base station (New radio node B, hereinafterNR gNB or NR base station) 2 c-10 and a new radio core network (NR CN) 2c-05. The user terminal (new radio user equipment, hereinafter, NR UE orUE) 2 c-15 accesses the external network through the NR gNB 2 c-10 andthe NR CN 2 c-05.

In FIG. 2C, the NR gNB (2 c-10) corresponds to an evolved node B (eNB)of the existing LTE system. The NR gNB is connected to the NR UE 2 c-15via a radio channel and may provide a service superior to the existingnode B. In the next generation mobile communication system, since alluser traffics are served through a shared channel, an apparatus forcollecting state information such as a buffer status, an availabletransmission power status, and a channel status of the UEs to performscheduling is used. The NR NB 2 c-10 may serve as the apparatus. One NRgNB generally controls a plurality of cells. In order to realizehigh-speed data transmission compared with the current LTE, the NR gNBmay have an existing maximum bandwidth or more, and may be additionallyincorporated into a beam-forming technology may be applied by usingorthogonal frequency division multiplexing (hereinafter, referred to asOFDM) as a radio access technology. Further, an adaptive modulation &coding (hereinafter, referred to as AMC) determining a modulation schemeand a channel coding rate according to a channel status of the terminalis applied. The NR CN 2 c-05 may perform functions such as mobilitysupport, bearer setup, QoS setup, and the like. The NR CN is anapparatus for performing a mobility management function for the terminaland various control functions and is connected to a plurality of basestations. In addition, the next generation mobile communication systemcan interwork with the existing LTE system, and the NR CN is connectedto the MME 2 c-25 through the network interface. The MME is connected tothe eNB 2 c-30 which is the existing base station.

FIG. 2D is a diagram illustrating the radio protocol structure of thenext generation mobile communication system to which the presentdisclosure may be applied.

Referring to FIG. 2D, the radio protocol of the next generation mobilecommunication system is configured to include NR PDCPs 2 d-05 and 2d-40, NR RLCs 2 d-10 and 2 d-35, and NR MACs 2 d-15 and 2 d-30 in theterminal and the NR base station. The main functions of the NR PDCPs 2d-05 and 2 d-40 may include some of the following functions.

-   -   Header compression and decompression function (Header        compression and decompression: ROHC only)    -   Transfer function of user data (Transfer of user data)    -   In-sequence delivery function (In-sequence delivery of upper        layer PDUs)    -   Reordering function (PDCP PDU reordering for reception)    -   Duplicate detection function (Duplicate detection of lower layer        SDUs)    -   Retransmission function (Retransmission of PDCP SDUs)    -   Ciphering and deciphering function (Ciphering and deciphering)    -   Timer-based SDU discard function (Timer-based SDU discard in        uplink)

In this case, the reordering function of the NR PDCP apparatus refers toa function of reordered PDCP PDUs received in a lower layer in orderbased on a PDCP sequence number (SN) and may include a function oftransferring data to the upper layer in the reordered order, a functionof recording PDCP PDUs missed by the reordering, a function of reportinga state of the missed PDCP PDUs to a transmitting side, and a functionof requesting a retransmission of the missed PDCP PDUs.

The main functions of the NR RLCs 2 d-10 and 2 d-35 may include some ofthe following functions.

-   -   Data transfer function (Transfer of upper layer PDUs)    -   In-sequence delivery function (In-sequence delivery of upper        layer PDUs)    -   Out-of-sequence delivery function (Out-of-sequence delivery of        upper layer PDUs)    -   ARQ function (Error correction through HARQ)    -   Concatenation, segmentation, reassembly function (Concatenation,        segmentation and reassembly of RLC SDUs)    -   Re-segmentation function (Re-segmentation of RLC data PDUs)    -   Reordering function (Reordering of RLC data PDUs)    -   Duplicate detection function (Duplicate detection)    -   Error detection function (Protocol error detection)    -   RLC SDU discard function (RLC SDU discard)    -   RLC re-establishment function (RLC re-establishment)

In this case, the in-sequence delivery function of the NR RLC apparatusrefers to a function of delivering RLC SDUs received from a lower layerto an upper layer in order, and may include a function of reassemblingand transferring an original one RLC SDU which is divided into aplurality of RLC SDUs and received. The NR RLC may include a function ofreorder the received RLC PDUs based on the RLC sequence number (SN) orthe PDCP sequence number (SN) and a function of recording the RLC PDUsmissed by the reordering. The NR RLC may include a function of reportinga state of the missed RLC PDUs to the transmitting side and a functionof requesting a retransmission of the missed RLC PDUs. The NR RLC mayinclude a function of transferring only the SLC SDUs before the missedRLC SDU to the upper layer in order when there is the missed RLC SDU anda function of transferring all the received RLC SDUs to the upper layerbefore a predetermined timer starts if the timer expires even if thereis the lost RLC SDU. Alternatively, the NR RLC may include a function oftransferring all the RLC SDUs received until now to the upper layer inorder if the predetermined timer expires even if there is the missed RLCSDU. Further, the NR RLC may process the RLC PDUs in the received order(in order of arrival regardless of the order of a serial number and thesequence number), and may transmit the processed RLC PDUs to the PDCPapparatus the out-of-sequence delivery. In the case of the segment, theNR RLC may receive the segments which are stored in the buffer or is tobe received later and reconfigure the RLC PDUs into one complete RLC PDUand then transmit the complete RLC PDU to the PDCP apparatus. The NR RLClayer may not include the concatenation function and may perform thefunction in the NR MAC layer or may be replaced by the multiplexingfunction of the NR MAC layer.

In this case, the out-of-sequence delivery function of the NR RLCapparatus refers to a function of directly delivering the RLC SDUsreceived from the lower layer to the upper layer regardless of order.The NR RLC may include a function of reassembling and transferring anoriginal one RLC SDU which is divided into several RLC SDUs andreceived, and a function of storing and reordering the RLC SN or thePDCP SP of the received RLC PDUs to record the missed RLC PDUs.

The NR MACs 2 d-15 and 2 d-30 may be connected to several NR RLC layerapparatus configured in one terminal, and the main functions of the NRMAC may include some of the following functions.

-   -   Mapping function (Mapping between logical channels and transport        channels)    -   Multiplexing and demultiplexing function        (Multiplexing/demultiplexing of MAC SDUs)    -   Scheduling information reporting function (Scheduling        information reporting)    -   HARQ function (Error correction through HARQ)    -   Priority handling function between logical channels (Priority        handling between logical channels of one UE)    -   Priority handling function between terminals (Priority handling        between UEs by means of dynamic scheduling)    -   MBMS service identification function (MBMS service        identification)    -   Transport format selection function (Transport format selection)    -   Padding function (Padding)

The NR PHY layers 2 d-20 and 2 d-25 may perform an operation ofchannel-coding and modulating an upper layer data, making the upperlayer data as an OFDM symbol and transmitting them to a radio channel,or demodulating and channel-decoding the OFDM symbol received throughthe radio channel and transmitting the demodulated and channel-decodedOFDM symbol to the upper layer.

FIGS. 2EA-2EB are diagrams illustrating a structure of processing datain the LTE system.

As shown in FIGS. 2EA-2EB, in the LTE system, the data processing isperformed in the PDCP layer and the RLC layer for each logical channel.That is, the logical channel 1 2 e-05 and the logical channel 2 2 e-10have different PDCP layers and RLC layers and perform independent dataprocessing. Then, the RLC PDU generated from the RLC layer of eachlogical channel is transmitted to the MAC layer, which is configured asone MAC PDU, and then transmitted to the receiving end. In the LTEsystem, the PDCP layer, the RLC layer, and the MAC layer may include thefunctions described with reference to FIG. 2B, and may performcorresponding operations.

The LTE system may be characterized in that the PDCP PDUs concatenate inthe RLC layer and in the MAC PDU structure as shown in 2 e-25, all theMAC subheaders are located at the head part and the MAC SDU part islocated at the tail part of the MAC PDU. Due to the abovecharacteristics, in the LTE system, the data processing may be performedin advance or prepared in the RLC layer before the uplink transmissionresource (uplink grant) is received. If receiving the uplinktransmission resource 2 e-30 as shown in FIGS. 2EA-2EB, the terminalconcatenates the PDCP PDUs received from the PDCP layer according to theuplink transmission resource to generate the RLC PDU. The uplinktransmission resources are received from the base station in the MAClayer and then subjected to logical channel prioritization (LCP), andthe uplink transmission resources are allocated to each logical channel.That is, the uplink transmission resource 2 e-30 is the uplinktransmission resource allocated from the MAC layer. If the size of thePDCP PDUs to be concatenated does not match the uplink transmissionresource, the RLC layer performs a segmentation procedure to match thePDCP PDUs with the uplink transmission resources. The above proceduremay be performed for each logical channel, and each RLC apparatus canconfigure an RLC header using the concatenated PDCP PDUs and transmitthe completed RLC PDU to the MAC apparatus. The MAC apparatus mayconfigure the RLC PDUs (MAC SDUs) received from each RLC layer as oneMAC PDU and transmit the MAC PDU to the PHY apparatus. When the RLCapparatus performs a segmentation operation when configuring the RLCheader and includes the segmented information in the header, the MACapparatus may include the length information of each of the concatenatedPDCP PDUs in the header (which is to be reassembled at the receivingend).

As described above, in the LTE system, the data processing of the RLClayer, the MAC layer, and the PHY layer starts from the time when theuplink transmission resource is received.

In the LTE system, the RLC layer may operate in an RLC acknowledged mode(AM) mode, an RLC unacknowledged mode (UM) mode, and an RLC transparentmode (TM) mode. In the RLC AM mode, the RLC layer supports the ARQfunction, the transmitting end may receive the RLC status report fromthe receiving end and perform the retransmission on the RLC PDUs thatreceive the NACK through the status report. Accordingly, reliable datatransmission may be achieved without error. Therefore, it is suitablefor a service requiring high reliability. On the other hand, the ARQfunction is not supported in the RLC UM mode. Therefore, the RLC statusreport is not received and there is no retransmission function. In theRLC UM mode, when the uplink transmission resource is received, thetransmitting end RLC layer concatenates the PDCP PDUs (RLC SDUs)received from the upper layer and transmits the received PDCP PDUs tothe lower layer. Therefore, the data can be continuously transmittedwithout the transmission delay and can be useful for a service sensitiveto the transmission delay. In the RLC TM mode, the RLC layer directlytransmits the PDCP PDUs received from the upper layer to the lower layerwithout performing any processing. That is, in the TM mode of the RLClayer, the data from the upper layer is transparently transmitted to thelower layer in the RLC layer. Therefore, it can be useful fortransmitting system information, paging message, or the like transmittedon a common channel such as a common control channel (CCCH).

FIGS. 2FA-2FB are diagrams illustrating a structure of processing datain the next generation mobile communication system of the presentdisclosure.

As shown in FIGS. 2FA-2FB, in the next generation mobile communicationsystem, the data processing is performed in the PDCP layer and the RLClayer for each logical channel. That is, the logical channel 1 2 f-05and the logical channel 2 2 f-10 have different PDCP layers and RLClayers and perform independent data processing. Then, the RLC PDUgenerated from the RLC layer of each logical channel is transmitted tothe MAC layer, which is configured as one MAC PDU, and then transmittedto the receiving end. In the LTE system, the PDCP layer, the RLC layer,and the MAC layer may include the functions described with reference toFIG. 2D, and may perform corresponding operations.

The next generation mobile communication system may be characterized inthat the PDCP PDUs concatenate in the RLC layer and in the MAC PDUstructure as shown in 2 e-25, the MAC subheaders have for each MAC SDU,that is, are repeated in units of the MAC sub-header and the MAC SDU.Therefore, in the next generation mobile communication system, as shownin 2 f-30, the data may be pre-processed in advance before receiving theuplink transmission resource. That is, if the terminal receives an IPpacket from the PDCP layer before receiving the UL grant, the terminalmay perform the PDCP processing (ciphering, integrity protection, or thelike) on the IP packet, generate a PDCP header to generate the PDCP PDU,and transmit the PDCP PDU to the RLC layer to configure the RLC header,and transmit the RLC PDU to the MAC layer to configure the MAC subheaderand the MAC SDU in advance.

If the terminal receives the uplink transmission resource 2 f-30, theterminal may configure the MAC PDU by fetching the MAC subheaders andthe MAC SDUs corresponding to the size of the uplink transmissionresource, and if the uplink transmission resource is not sufficient, thesegmentation operation may be performed to fully fill and efficientlyuse the transmission resources. Then, the corresponding RLC header(segmented information or length information) and MAC header (since theL field and length are changed) can be updated (2 f-40). Therefore,assuming that the NR system receives the uplink transmission resourcesat the same time points 2 f-30 and 2 f-45 as compared with the LTEsystem, the next generation mobile communication system may have a largegain in a processing time like 2 f-35. The RLC layer and the PDCP layermay use a common serial number if necessary or when configured by anetwork.

The pre-processing operation may be performed for each logical channel,and the RLC PDUs pre-processed for each logical channel may bepre-processed to MAC SDUs and MAC subheaders in the MAC layer. Inaddition, if the MAC layer receives the uplink transmission resource (2f-30), the terminal may allocate the uplink transmission grant to eachlogical channel and multiplex the MAC SDUs and MAC sub-headers generatedin advance. After receiving the uplink transmission resource from thebase station, the terminal performs the logical channel prioritization(LCP) in the MAC layer, and allocates the uplink transmission resourcesto each logical channel. The terminal multiplexes the MAC SDUs and theMAC subheaders generated for each logical channel to form one MAC PDUand transmits the MAC PDU to the PHY layer. If the uplink transmissionresources allocated to each logical channel are insufficient, theterminal may perform the segmentation request to the RLC layer and ifthe segmentation operation is performed in the RLC layer, the terminalincludes the segmented information in the header and updates thesegmented information and transmits the segmented information to the MAClayer again, in which the MAC layer may update the MAC headercorresponding thereto. That is, the next generation mobile communicationsystem starts the data processing of the PDCP layer, the RLC layer, andthe MAC layer starts before receiving the uplink transmission resource.

Since the next generation mobile communication system has theabove-mentioned structure, several RLC PDUs may enter one MAC PDU. Sincethere is a concatenation function in the RLC layer in the LTE system, aplurality of PDCP PDUs are concatenated to form one RLC PDU, which is inturn transmitted to the MAC layer. Therefore, one MAC PDU usuallyincludes RLC PDUs corresponding to the number of logical channels (inthe LTE system, the number of logical channels is generally about 2 to4). However, in the next generation mobile communication system, onePDCP PDU is generated as one RLC PDU since there is no RLC concatenationfunction in the RLC layer. Therefore, the RLC PDUs may be included inone MAC PDU by the number obtained by multiplying the IP packet (PDCPSDU) by the number of logical channels. In a simple arithmeticcalculation, at most four RLC PDUs may be included in one MAC PDU in theLTE system, while in the next generation mobile communication system,more than 500 RLC PDUs may be included in one MAC PDU. Therefore, in thenext generation mobile communication system, if one MAC PDU is missed,it is necessary to retransmit several hundred RLC PDUs.

By the way, in the LTE system, when the missed RLC PDUs are reported tothe transmitting end, a serial number of the missed RLC PDUs istransmitted by being included in the RLC status report one by one.Therefore, if RLC PDUs having a serial number of 500 are missed, a largeoverhead is used because 500 RLC serial numbers should be transmitted bybeing included in the RLC status report, and the transmitting endrequires a lot of processing time to interpret them.

Therefore, the present disclosure proposes a method of reporting an RLCstatus suitable for a next generation mobile communication system. Thecore idea of the present disclosure is characterized in that the missedregion is indicated and reported for the RLC PDUs consecutively missed.For example, if Nos. 400 to 700 are missed, it may be transmitted to thetransmitting end that up to No. 399 may be received well and up to 300numbers starting from No. 400 are missed.

FIG. 2G is a diagram illustrating a first method of reporting an RLCstatus according to the present disclosure.

FIG. 2G is a diagram illustrating an example of an RLC status reporttransmitted from a receiving side RLC layer apparatus to a transmittingside RLC layer apparatus according to the first method of reporting anRLC status according to the present disclosure (assuming a 12-bit RLC SNlength, 16-bit SOstart and SOend). In this case, the RLC SN length, theSOstart and the SOend length may be changed and replaced with apredetermined length.

The receiving side RLC layer device stores the received RLC PDUs in thereceiving buffer and then checks the serial number to recognize theserial number of the RLC PDU missed during the transmission. If thepredetermined condition is satisfied, the receiving side RLC layerapparatus generates an RLC status report message and transmits thegenerated RLC status report message to the transmitting side RLC layerapparatus. The predetermined condition may be a case where polling isreceived from the transmitting side RLC layer device, that is, the pollbit is set to be ‘1’ in the RLC header of the received RLC PDU. The RLCstatus report message includes information on the RLC PDU receptionstate of the receiving side RLC layer apparatus, and the transmittingside RLC layer apparatus identifies the RLC PDU successfully transmittedand the RLC PDU failed to transmit, through the RLC status reportmessage. The RLC status report message may be written like 2 g-05 inFIG. 2G. The RLC status report message includes one ACK_SN or one ACK_SNand one or more NACK. The presence of NACK_SN is indicated by an E1field. The E1 field indicates whether one NACK_SN, an E1 field, and anE2 field follow, and the E2 field indicates whether or not SOstart andSOend fields indicating a part of the NACK_SN follow. The ACK_SN fieldincludes the serial number subsequent to the highest serial number amongthe serial numbers of RLC PDUs successfully received so far and theNACK_SN includes the serial numbers of the RLC PDUs that have not beenreceived. For example, the transmitting side RLC layer apparatustransmits RLC PDU [7] to RLC PDU [10] at any time, and the receivingside RLC layer apparatus receives only RLC PDU [7] and RLC PDU [9] andstores the received RLC PDU [7] and RLC PDU [9] in the receiving buffer.If the RLC status report message generation condition is satisfied atany time, the receiving side RLC layer apparatus generates the RLCstatus report message. A serial number 10 is included in the ACK_SNfield of the RLC status report message, and a serial number 8 isincluded in the NACK_SN field. The transmitting side RLC layer apparatusreceiving the RLC status report message determines that the RLC PDUhaving a serial number lower than the lowest NACK_SN, that is, the RLCPDUs having a serial number lower than 7 is successfully transmitted anddiscards it in a retransmitting buffer. In addition, PDCP SDUs mapped tothe RLC PDUs having a serial number lower than 7 among the PDCP SDUsstored in the transmission buffer is also discarded. The transmittingside RLC layer apparatus retransmits the RLC PDU [8] reporting that thereceiving side RLC layer apparatus has not received.

The RLC layer apparatus transmits the RLC PDU with the serial number,and checks whether the transmitted RLC PDU succeeds based on the RLCstatus report message and retransmits the RLC PDU, thereby ensuringreliable transmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of information.

-   -   Identify RLC PDU failing to transmit    -   Identify RLC PDU failing to transmit

The transmitting side RLC layer apparatus is recognized which RLC PDU toretransmit in the future by identifying the RLC PDU failing to transmit,and it determines which RLC PDU or PDCP SDU of RLC PDUs or PDCP SDUsstored in the retransmission buffer and the transmission buffer isdiscarded.

The fields applied to the first method of reporting an RLC statusaccording to the present disclosure are as follows.

-   -   The D/C field has a length of 1 bit and indicates whether the        RLC PDU is an RLC data PDU or an RLC control PDU. (Table 1-16).

TABLE 1 D/C field value Description 0 Control PDU 1 Data PDU

-   -   The CPT field has a length of 3 bit and indicates a kind of RLC        control PDU. (Table 1-9).

TABLE 2 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

-   -   ACK_SN indicates the next serial number of the RLC PDU that has        not yet been received and a serial number that is not reported        as missed in the RLC status report. When the transmitting end        receives the RLC status report, the transmitting end is        determined that the serial number indicated by the ACK_SN and        the serial number indicated by the NACK_SN are excluded, and a        serial number smaller than ACK_SN has been received successfully        (when the NACK_SN is indicated together with the SOstart and the        SOend, it is determined that the SOstart and the SOend        successfully receive only a part other than the part indicated        by the NACK_SN). The ACK_SN has a predetermined length, and the        predetermined length can be variously defined such as 10 bits,        16 bits, and 18 bits.    -   The E1 field has a length of 1 bit and indicates whether or not        the NACK_SN, the E1 field, and the E2 field follow.

TABLE 3 E1 field value Description 0 A set of NACK_SN, E1 and E2 doesnot follow. 1 A set of NACK_SN, E1 and E2 follows.

-   -   NACK_SN indicates the serial number of the missed RLC PDU, and        may indicate a part of the missed RLC PDU together with SOstart        and SOend. The NACK_SN has a predetermined length, and the        predetermined length can be variously defined such as 10 bits,        16 bits, or 18 bits.    -   The E2 field has a length of 1 bit and indicates whether the        SOstart and the SOend follow. (Table 1-19).

TABLE 4 E2 field value Description 0 A set of SOstart and SOend does notfollow for this NACK_SN. 1 A set of SOstart and SOend follows for thisNACK_SN.

-   -   The SOstart field indicates a head location of the part when        indicating a part of the NACK_SN. When the head location is        indicated, it may be indicated by units of byte. The SOstart has        a predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.    -   The SOend field indicates a tail location of the part when        indicating a part of the NACK_SN. When the tail location is        indicated, it may be indicated by a byte unit. The SOend has a        predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.

In order to apply the method for reporting a first RLC status describedabove, a format such as 2 g-05 may be used. In order to facilitateprocessing in units of bytes, a reservation field such as 2 g-10 is usedor added so that the RLC status report format can be uniformly generatedin units of bytes. Although the length of the RLC serial number and thelength of the SOstart and the SOend are set to be different lengths, theRLC status report format may be configured in units of byte by setting(using and adding) the reserved field. That is, when the RLC statusreport is transmitted, the transmitting end RLC layer generates the RLCstatus report in units of byte, and the receiving end may quickly readand analyze the RLC status report in units of byte.

FIGS. 2HA-2HB are diagrams illustrating a second method of reporting anRLC status according to the present disclosure.

FIGS. 2HA-2HB are diagrams illustrating an example of an RLC statusreport transmitted from a receiving side RLC layer apparatus to atransmitting side RLC layer apparatus according to the second method ofreporting an RLC status according to the present disclosure (assuming a12-bit RLC SN length, 16-bit SO start and SOend).

The receiving side RLC layer device stores the received RLC PDUs in thereceiving buffer and then checks the serial number to recognize theserial number of the RLC PDU missed during the transmission. If thepredetermined condition is satisfied, the receiving side RLC layerapparatus generates an RLC status report message and transmits thegenerated RLC status report message to the transmitting side RLC layerapparatus. The predetermined condition may be a case where polling isreceived from the transmitting side RLC layer device, that is, the pollbit is set to be ‘1’ in the RLC header of the received RLC PDU. The RLCstatus report message includes information on the RLC PDU receptionstate of the receiving side RLC layer apparatus, and the transmittingside RLC layer apparatus identifies the RLC PDU successfully transmittedand the RLC PDU failed to transmit, through the RLC status reportmessage. The RLC status report message may be written like 2 h-05 inFIGS. 2HA-2HB. The RLC status report message includes one ACK_SN or aset of one ACK_SN and one or more NACK_SN, E1, E2, and E3 fields. It isindicated by the E1 field whether there are the set of NACK_SN, E1, E2,and E3 fields. The E1 field indicates whether a set of one NACK_SNfield, the E1 field, the E2 field, and the E3 field follow, and the E2field indicates whether or not SOstart and SOend fields indicating apart of the NACK_SN follow. The E3 field indicates whether there areNACK_RANGE (number of missing RLC PDUs) fields indicating how manyserial numbers above (larger) or below (smaller) from the serial numberindicated by the NACK_SN are missed. The NACK_RANGE field is a fieldindicating how many serial numbers above (having larger serial number)or below (having smaller serial number) from the serial number indicatedby the NACK_SN are missed.

The ACK_SN field may include the serial number sequent to the highestsequence number among the serial numbers of RLC PDUs that havesuccessfully received so far and the NACK_SN may include the serialnumber that has not successfully received so far. When a plurality ofconsecutive RLC PDUs are missed, the highest sequence number that hasnot been received so far or the lowest serial number that has not beenreceived so far can be included in the NACK_SN in order to use NACK_SNtogether with the NACK_RANGE field, and the N field may include thenumber of missed serial numbers. The NACK_SN and NACK_RANGE fields maybe defined and applied by various other methods to indicate a number ofRLC PDUs that have been missed consecutively.

The missing of RLC PDUs can occur in a variety of ways.

First, individual RLC PDUs may be missed. That is, it may be necessaryto indicate the serial number of the missed independent RLC PDU (2h-05). The individual RLC PDUs indicate the RLC serial number of theindividual RLC PDU as the NACK_SN like 2 h-10, and set E1 to 1 toindicate another missed packet behind. Since there is no need toindicate segment, E2 is set to be 0, and since there is no need toindicate the regions for several missed RLC PDUs, E3 may be set to be 0to indicate that the individual RLC PDU has been missed like 2 h-05.

Second, segments of individual RLC PDUs may be missed. That is, it maybe necessary to indicate the serial number of the missed independent RLCPDU segment (2 h-10). In this case, the segments of the RLC PDUsindividually indicate the RLC serial numbers of the individual RLC PDUsas the NACK_SN like 2 h-10, and E2 is set to be 1 to indicate thesegment to indicate that the SOstart field and the SOend field followand uses the SOstart Field and the SOend field to indicate the segmentlocation of the corresponding RLC PDU. In order to indicate anothermissed packet behind, E1 is set to be 1, and since the regions for theplurality of missed RLC PDUs are not indicated, E3 may be set to be 0 toindicate the segments of the individual RLC PDUs are missed like 2 h-10.

Third, a number of consecutive RLC PDUs may be missed at once. That is,it may be necessary to indicate a number of consecutive RLC PDUs at once(2 h-15). A number of consecutive RLC PDUs indicate, by the NACK_SN, RLCserial numbers of an individual RLC PDU corresponding to the lowestserial number or the highest serial number like 2 h-15, and in order toindicate regions for a number of RLC PDUs consecutively missed, E3 maybe set to be 1 to indicate that the NACK_RANGE field follows andindicate the regions for the corresponding consecutive RLC PDUs usingthe NACK_RANGE field. In this case, the NACK_RANGE field may indicatehow many the consecutive NACK_SNs have been missed. Then, to indicateanother missed packet, E1 may be set to be 1. Since there is no need toindicate the segment, E2 may be set to be 0 to indicate that theplurality of RLC PDUs are missed consecutively like 2 h-15.

Fourth, the last segment of one RLC PDU, a number of RLC PDUsconsecutive thereafter, and a first segment of one RLC PDU consecutivethereafter may be missed at once (2 h-20-1). In this case, a lastsegment of one RLC PDU, a number of RLC PDUs consecutive thereafter, anda first segment of one RLC PDU consecutive thereafter indicate the firstand last segments in the same manner as 2 h-10 and a number ofconsecutive RLC PDUs are indicated in the same manner as 2 h-15, whichmay be reported to the transmitting end.

Fifth, the last segment of one RLC PDU and a number of RLC PDUsconsecutive thereafter may be missed at once (2 h-20-2). In this case,the last segment of one RLC PDU and a number of RLC PDUs consecutivethereafter indicate the first segment in the same manner as 2 h-10 and anumber of consecutive RLC PDUs are indicated in the same manner as 2h-15, which may be reported to the transmitting end.

Sixth, a number of consecutive RLC PDUs and the first segment of anumber of RLC PDUs consecutive thereafter may be missed at once (2h-20-3). In this case, a number of consecutive RLC PDUs and a firstsegment of one RLC PDU consecutive thereafter indicate the last segmentin the same manner as 2 h-10 and a number of consecutive RLC PDUs areindicated in the same manner as 2 h-15, which may be reported to thetransmitting end.

In order to apply the second method for reporting an RLC statusdescribed above, a format such as 2 h-01 may be used. In order tofacilitate processing in units of bytes, a reservation field such as 2h-02 is used or added so that the RLC status report format can beuniformly generated in units of bytes. Although the length of the RLCserial number and the length of the SOstart and the SOend are set to bedifferent lengths, the RLC status report format may be configured inunits of byte by setting (using and adding) the reserved field. That is,when the RLC status report is transmitted, the transmitting end RLClayer generates the RLC status report in units of byte, and thereceiving end may quickly read and analyze the RLC status report inunits of byte.

When the RLC status report is performed at the receiving end, if thetransmission resources are insufficient, it may not include all thereport information to be indicated as 2 h-05, 2 h-10, and 2 h-15.Therefore, if the transmission resources are insufficient, a method ofindicating a larger number of missed RLC PDUs with the same transmissionresource should be used first to perform a report. That is, if the 2h-15 method may be applied to the RLC PDUs that should be reported to bemissed, the 2 h-15 method is firstly applied to perform the report,followed by the 2 h-05 method, and then the 2 h-10 method can be appliedto perform the report.

As an example of the application method in an embodiment, the receivingend RLC apparatus may request the retransmission to the transmitting endRLC apparatus since the RLC PDUs corresponding to all the serial numbersbetween 2<serial number 8 as NACK SN=8, N=6 are missed. As anotherexample, the transmitting side RLC layer apparatus transmits RLC PDU [5]to RLC PDU [80] at any time, and the receiving side RLC layer apparatusreceives only RLC PDU [5], RLC PDU [78], RLC PDU [79], and RLC PDU [80]and stores the received RLC PDU [5], RLC PDU [78], RLC PDU [79], and RLCPDU [80] in the receiving buffer. If the RLC status report messagegeneration condition is satisfied at any time, the receiving side RLClayer apparatus generates the RLC status report message. The ACK_SNfield of the RLC status report message may include the serial number 81,the NACK_SN field may include the serial number 6, and another NACK_SNfield may include 69 in the N field together with the serial number 8(6, serial number 77). The transmitting side RLC layer apparatusreceiving the RLC status report message determines that the RLC PDUhaving a serial number lower than the lowest NACK_SN, that is, the RLCPDUs having a serial number lower than 6 is successfully transmitted anddiscards it in a retransmitting buffer. In addition, PDCP SDUs mapped tothe RLC PDUs having a serial number lower than 6 among the PDCP SDUsstored in the transmission buffer is also discarded. The transmittingside RLC layer apparatus retransmits the RLC PDU [6] to RLC PDU [8] toRLC PDU [77] reporting that the receiving side RLC layer apparatus hasnot received.

The RLC layer apparatus transmits the RLC PDU with the serial number,and checks whether the transmitted RLC PDU succeeds based on the RLCstatus report message and retransmits the RLC PDU, thereby ensuringreliable transmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of informationlargely.

-   -   Identify RLC PDU failing to transmit    -   Identify RLC PDU failing to transmit

The transmitting side RLC layer apparatus is recognized which RLC PDU toretransmit in the future by identifying the RLC PDU failing to transmit,and it determines which RLC PDU or PDCP SDU of RLC PDUs or PDCP SDUsstored in the retransmission buffer and the transmission buffer isdiscarded.

The fields applied to the second method of reporting an RLC statusaccording to the present disclosure are as follows.

-   -   The D/C field has a length of 1 bit and indicates whether the        RLC PDU is an RLC data PDU or an RLC control PDU. (Table 1-16).

TABLE 5 D/C field value Description 0 Control PDU 1 Data PDU

-   -   The CPT field has a length of 3 bit and indicates a kind of RLC        control PDU. (Table 1-9).

TABLE 6 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

-   -   ACK_SN indicates the next serial number of the RLC PDU that has        not yet been received and a serial number that is not reported        as missed in the RLC status report. When the transmitting end        receives the RLC status report, the transmitting end determined        that the serial number indicated by the ACK_SN and the serial        numbers included in the ranged indicated by the NACK_SN and the        NACK_RANGE field are excluded, and a serial number smaller than        ACK_SN has been received successfully (when the NACK_SN is        indicated the SOstart and the SOend together, it is determined        that the SOstart and the SOend successfully receive only a part        other than the part indicated by the NACK_SN). The ACK_SN has a        predetermined length, and the predetermined length can be        variously defined such as 12 bits, 16 bits, and 18 bits.    -   The E1 field has a length of 1 bit and indicates whether or not        the NACK_SN, the E1 field, the E2 field, and the E3 field        follow.

TABLE 7 E1 field value Description 0 A set of NACK_SN, E1, E2, and E3does not follow. 1 A set of NACK_SN, E1, E2, and E3 follows.

The NACK_SN may include the serial number that has not received so far.When a plurality of consecutive RLC PDUs are missed, the highestsequence number that has not been received so far or the lowest serialnumber that has not been received so far can be included in the NACK_SNin order to use NACK_SN together with the NACK_RANGE field, and the Nfield may include the number of missed serial numbers. The NACK_SN andNACK_RANGE fields may be defined and applied by various other methods toindicate a number of RLC PDUs that have been missed consecutively. TheNACK_SN has a predetermined length, and the predetermined length can bevariously defined such as 12 bits, 16 bits, or 18 bits.

The NACK_RANGE field is a field indicating how many serial numbers above(having larger serial number) or below (having smaller serial number)from the serial number indicated by the NACK_SN are missed.

-   -   The E2 field has a length of 1 bit and indicates whether the        SOstart and the SOend follow. (Table 1-19).

TABLE 8 E2 field value Description 0 A set of SOstart and SOend does notfollow for this NACK_SN. 1 A set of SOstart and SOend follow for thisNACK_SN.

-   -   The SOstart field indicates a head location of the part when        indicating a part of the NACK_SN. When the head location is        indicated, it may be indicated by units of byte. The SOstart has        a predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.    -   The SOend field indicates a tail location of the part when        indicating a part of the NACK_SN. When the tail location is        indicated, it may be indicated by a byte unit. The SOend has a        predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.

The E3 field indicates whether there are NACK_RANGE (number of missingRLC PDUs) fields indicating how many serial numbers above (larger) orbelow (smaller) from the serial number indicated by the NACK_SN aremissed.

TABLE 9 E3 field value Description 0 NACK_RANGE does not follow for thisNACK_SN. 1 NACK_RANGE follows for this NACK_SN.

FIGS. 2IA-2IC are diagrams illustrating a third method of reporting anRLC status according to the present disclosure.

FIGS. 2IA-2IC are diagrams illustrating an example of an RLC statusreport transmitted from a receiving side RLC layer apparatus to atransmitting side RLC layer apparatus according to the third method ofreporting an RLC status according to the present disclosure (assuming a12-bit RLC SN length, 16-bit SO start and SOend). The third method forreporting an RLC status additionally proposes and applies a method thatcan reduce the overhead over the second method for reporting an RLCstatus.

The receiving side RLC layer device stores the received RLC PDUs in thereceiving buffer and then checks the serial number to recognize theserial number of the RLC PDU missed during the transmission. If thepredetermined condition is satisfied, the receiving side RLC layerapparatus generates an RLC status report message and transmits thegenerated RLC status report message to the transmitting side RLC layerapparatus. The predetermined condition may be a case where polling isreceived from the transmitting side RLC layer device, that is, the pollbit is set to be ‘1’ in the RLC header of the received RLC PDU. The RLCstatus report message includes information on the RLC PDU receptionstate of the receiving side RLC layer apparatus, and the transmittingside RLC layer apparatus identifies the RLC PDU successfully transmittedand the RLC PDU failed to transmit, through the RLC status reportmessage. The RLC status report message may be written like 2 i-01 inFIGS. 2IA-2IC. The RLC status report message includes one ACK_SN or aset of one ACK_SN and one or more NACK_SN, E1, E2, and E3 fields. It isindicated by the E1 field whether there are the set of NACK_SN, E1, E2,and E3 fields. The E1 field indicates whether a set of one NACK_SNfield, the E1 field, the E2 field, and the E3 field follow, and the E2field indicates whether or not SOstart and SOend fields indicating apart of the NACK_SN follow when the E3 field indicates that theNACK_RANGE field does not follow to indicate only one NACK_SN. However,if the E2 field indicates whether the SOstart field and the SOend fieldindicating the segment information on the head part and the tail part ofthe NACK_RANGE follow when the E3 field indicates that the NACK_RANGEfield follows. In this case, it can be promised that if the E2 fieldindicates that the SOstart field and the SOend field follow and the E3field indicates that the NACK_RANGE field exists, the NACK_RANGE fieldfollows just after the NACK_SN and the SO field and the SOend fieldfollow thereafter. If the E3 field indicates that the NACK_RANGE fieldfollows and the E2 field indicates that the SOstart field and the SOendfield follow, the SOstart field and the SOend field may indicateinformation different from the information indicating the NACK_SN whenthere is no NACK_RANGE. That is, the SOstart field is informationindicating whether in the RLC PDU having a serial number which isNACK_SN−1, a segment starts from any location of an original RLC PDU andis segmented to the end, and the SOend field is information indicatingwhether in the RLC PDU having a serial number which isNACK_SN+NACK_RANGE, a segment starts from any location of an originalRLC PDU and is segmented up to any location. The information indicatedby these fields is defined and promised, and conversely, may be definedas follows. For example, the SOend field is information indicatingwhether in the RLC PDU having a serial number which is NACK_SN−1, asegment starts from any location of an original RLC PDU and is segmentedto the end, and the SOstart field is information indicating whether inthe RLC PDU having a serial number which is NACK_SN+NACK_RANGE, asegment starts from any location of an original RLC PDU and is segmentedup to any location.

The E3 field indicates whether there are NACK_RANGE (number of missingRLC PDUs) fields indicating how many serial numbers above (larger) orbelow (smaller) from the serial number indicated by the NACK_SN aremissed. The NACK_RANGE field is a field indicating how many serialnumbers above (having larger serial number) or below (having smallerserial number) from the serial number indicated by the NACK_SN aremissed.

The ACK_SN field may include the serial number sequent to the highestsequence number among the serial numbers of RLC PDUs that havesuccessfully received so far and the NACK_SN may include the serialnumber that has not successfully received so far. When a plurality ofconsecutive RLC PDUs are missed, the highest sequence number that hasnot been received so far or the lowest serial number that has not beenreceived so far can be included in the NACK_SN in order to use NACK_SNtogether with the NACK_RANGE field, and the N field may include thenumber of missed serial numbers. The NACK_SN and NACK_RANGE fields maybe defined and applied by various other methods to indicate a number ofRLC PDUs that have been missed consecutively.

The missing of RLC PDUs can occur in a variety of ways.

First, individual RLC PDUs may be missed. That is, it may be necessaryto indicate the serial number of the missed independent RLC PDU (2i-05). The RLC PDUs of the individual RLC PDUs are designated as theNACK_SN having the RLC serial number of the individual RLC PDUs like 2i-05. In order to indicate another missed packet behind, E1 is set to be1, and since there is no need to indicate the segment, E2 is set to be 0and since there is no need to indicate the regions for the plurality ofmissed RLC PDUs, E3 may be set to be 0, thereby indicating that theindividual RLC PDU is missed like 2 i-05.

Second, segments of individual RLC PDUs may be missed. That is, it maybe necessary to indicate the serial number of the missed independent RLCPDU segment (2 j-10). The segments of the RLC PDUs individually indicatethe RLC serial numbers of the individual RLC PDUs as the NACK_SN like 2i-10, and E2 is set to be 1 to indicate the segment to indicate that theSOstart field and the SOend field follow, and uses the SOstart Field andthe SOend field to indicate the segment location of the correspondingRLC PDU. In order to indicate another missed packet behind, E1 is set tobe 1. Since the regions for the plurality of missed RLC PDUs is notindicated, E3 may be set to be 0 to indicate the segments of theindividual RLC PDUs are missed like 2 i-10.

Third, a number of consecutive RLC PDUs may be missed at once. That is,it may be necessary to indicate a number of consecutive RLC PDUs at once(2 i-15). A number of consecutive RLC PDUs indicate, by the NACK_SN, RLCserial numbers of an individual RLC PDU corresponding to the lowestserial number or the highest serial number like 2 i-15, and in order toindicate the regions for a number of RLC PDUs consecutively missed, E3may be set to be 1 to indicate that the NACK_RANGE field follows andindicate the regions for the corresponding consecutive RLC PDUs usingthe NACK_RANGE field. In this case, the NACK_RANGE field may indicatehow many the consecutive NACK_SNs have been missed. Then, to indicateanother missed packet, E1 may be set to be 1. Since there is no need toindicate the segment, E2 may be set to be 0 to indicate that theplurality of RLC PDUs are missed consecutively like 2 i-15.

Fourth, the last segment of one RLC PDU, a number of RLC PDUsconsecutive thereafter, and a first segment of one RLC PDUs consecutivethereafter may be missed at once (2 i-20-1). The last segment of one RLCPDU and a number of RLC PDUs consecutive thereafter and the firstsegment of one RLC PDU consecutive thereafter may be indicated by usingthe NACK_RANGE field, the SOstart field, and the SOend field togetherlike 2 i-20. That is, the SOstart field may indicate whether in the RLCPDU having a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU and is segmented to the end, and theSOend field may indicate whether in the RLC PDU having a serial numberwhich is NACK_SN+NACK_RANGE, a segment starts from any location of anoriginal RLC PDU and is segmented up to any location. Accordingly, thelast segment of one RLC PDU, a number of subsequent consecutive RLCPDUs, and the first segment of one of subsequent consecutive RLC PDUsindicate the first and last segments in the same manner as 2 i-10 and anumber of consecutive RLC PDUs are indicated in the same manner as 2i-15, which may be reported to the transmitting end.

Fifth, the last segment of one RLC PDU and a number of RLC PDUsconsecutive thereafter may be missed at once (2 i-20-2). The lastsegment of one RLC PDU and a number of RLC PDUs consecutive thereafterand the first segment of one RLC PDU consecutive thereafter may beindicated by using the NACK_RANGE field, the SOstart field, and theSOend field together like 2 i-20. That is, the SOstart field mayindicate whether in the RLC PDU having a serial number which isNACK_SN−1, a segment starts from any location of an original RLC PDU,and the SOend field may define, as a special value, a value having allzero as 000 . . . 0.0000 or a value having all 1 as 111 . . . 1111 toindicate that a segment of the RLC PDU having a serial number which isthe NACK_SN+NACK_RANGE is not missed but the complete RLC PDU is missed.Accordingly, the last segment of one RLC PDU and a number of RLC PDUsconsecutive thereafter indicate the first segment in the same manner as2 i-10 and a number of consecutive RLC PDUs are indicated in the samemanner as 2 i-15, thereby more reducing the overhead than the case ofthe reporting.

Sixth, a number of consecutive RLC PDUs and the first segment of anumber of RLC PDUs consecutive thereafter may be missed at once (2i-20-3). In this case, a number of consecutive RLC PDUs and a firstsegment of one RLC PDU consecutive may be indicated by using theNACK_RANGE field, the SOstart field, and the SOend field together like 2i-20. That is, the SOstart field defines, as a special value, a valuehaving all zero as 000 . . . 0.0000 or a value having all 1 as 111 . . .1111 to indicate that there is no missed segment in the RLC PDU having aserial number which is the NACK_SN−1, and the SOend field may indicatewhether in the RLC PDU having a serial number which isNACK_SN+NACK_RANGE, a segment starts from any location of an originalRLC PDU and is segmented up to any location. Therefore, a number ofconsecutive RLC PDUs and the first segment of one RLC PDU consecutivethereafter indicate the last segment in the same manner as 2 i-10 and anumber of consecutive RLC PDUs are indicated in the same manner as 2i-15, thereby more reducing the overhead than the case of the reporting.

In order to apply the third method for reporting an RLC status describedabove, a format such as 2 i-01 may be used. In order to facilitateprocessing in units of bytes, a reservation field such as 2 i-02 is usedor added so that the RLC status report format can be uniformly generatedin units of bytes. Although the length of the RLC serial number and thelength of the SOstart and the SOend are set to be different lengths, theRLC status report format may be configured in units of byte by setting(using and adding) the reserved field. That is, when the RLC statusreport is transmitted, the transmitting end RLC layer generates the RLCstatus report in units of byte, and the receiving end may quickly readand analyze the RLC status report in units of byte.

When the RLC status report is performed at the receiving end, if thetransmission resources are insufficient, it may not include all thereport information to be indicated as 2 i-05, 2 i-10, and 2 i-15.Therefore, if the transmission resources are insufficient, a method ofindicating a larger number of missed RLC PDUs with the same transmissionresource should be used first to perform a report. That is, if the 2i-15 method may be applied to the RLC PDUs that should be reported to bemissed, the 2 i-15 method is firstly applied to perform the report,followed by the 2 i-05 method, and then the 2 i-10 method can be appliedto perform the report. Also, if there are insufficient resources toreport 2 i-20, the reporting may be made by the 2 i-15 method, exceptthe SOstart field and the SOend field. In other words, if the resourcesare insufficient, the 2 i-15 method is preferentially applied to performthe reporting, and the 2 i-05 method may be considered, and theremaining methods may be considered.

The RLC layer apparatus transmits the RLC PDU with the serial number,and checks whether the transmitted RLC PDU succeeds based on the RLCstatus report message and retransmits the RLC PDU, thereby ensuringreliable transmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of informationlargely.

-   -   Identify RLC PDU failing to transmit    -   Identify RLC PDU failing to transmit

The transmitting side RLC layer apparatus is recognized which RLC PDU toretransmit in the future by identifying the RLC PDU failing to transmit,and it determines which RLC PDU or PDCP SDU of RLC PDUs or PDCP SDUsstored in the retransmission buffer and the transmission buffer isdiscarded.

The fields applied to the third method of reporting an RLC statusaccording to the present disclosure are as follows.

-   -   The D/C field has a length of 1 bit and indicates whether the        RLC PDU is an RLC data PDU or an RLC control PDU. (Table 1-16).

TABLE 10 D/C field value Description 0 Control PDU 1 Data PDU

-   -   The CPT field has a length of 3 bit and indicates a kind of RLC        control PDU. (Table 1-9).

TABLE 11 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

-   -   ACK_SN indicates the next serial number of the RLC PDU that has        not yet been received and a serial number that is not reported        as missed in the RLC status report. When the transmitting end        receives the RLC status report, the transmitting end determined        that the serial number indicated by the ACK_SN and the serial        numbers included in the ranged indicated by the NACK_SN and the        NACK_RANGE field are excluded, and a serial number smaller than        ACK_SN has been received successfully (when the NACK_SN is        indicated the SOstart and the SOend together, it is determined        that the SOstart and the SOend successfully receive only a part        other than the part indicated by the NACK_SN). The ACK_SN has a        predetermined length, and the predetermined length can be        variously defined such as 12 bits, 16 bits, and 18 bits.    -   The E1 field has a length of 1 bit and indicates whether or not        the NACK_SN, the E1 field, the E2 field, and the E3 field        follow.

TABLE 12 E1 field value Description 0 A set of NACK_SN, E1, E2, and E3does not follow. 1 A set of NACK_SN, E1, E2, and E3 follows.

The NACK_SN may include the serial number that has not received so far.When a plurality of consecutive RLC PDUs are missed, the highestsequence number that has not been received so far or the lowest serialnumber that has not been received so far can be included in the NACK_SNin order to use NACK_SN together with the NACK_RANGE field, and the Nfield may include the number of missed serial numbers. The NACK_SN andNACK_RANGE fields may be defined and applied by various other methods toindicate a number of RLC PDUs that have been missed consecutively. TheNACK_SN has a predetermined length, and the predetermined length can bevariously defined such as 12 bits, 16 bits, or 18 bits.

The NACK_RANGE field is a field indicating how many serial numbers above(having larger serial number) or below (having smaller serial number)from the serial number indicated by the NACK_SN are missed.

-   -   The E2 field has a length of 1 bit and indicates whether the        SOstart and the SOend follow. (Table 1-19). If the E3 field        indicates that there is the NACK_RANGE, it may be promised that        the NACK_SN is followed by the NACK_RANGE, followed by the        SOstart and SOend.

TABLE 13 E2 field value Description 0 A set of SOstart and SOend doesnot follow for this NACK_SN. 1 A set of SOstart and SOend follow forthis NACK_SN.

The E2 field indicates whether the SOstart and SOend fields indicating apart of the NACK_SN follow when indicating only one NACK_SN indicatingthat the NACK_RANGE field is not followed in the E3 field. However, ifthe E2 field indicates whether the SOstart field and the SOend fieldindicating the segment information on the head part and the tail part ofthe NACK_RANGE follow when the E3 field indicates that the NACK_RANGEfield follows. That is, the SOstart and SOend fields may indicatedifferent information according to whether the E3 field is configured.In this case, it can be promised that if the E2 field indicates that theSOstart field and the SOend field follow and the E3 field indicates thatthe NACK_RANGE field exists, the NACK_RANGE field follows just after theNACK_SN and the SO field and the SOend field follow thereafter. If theE3 field indicates that the NACK_RANGE field follows and the E2 fieldindicates that the SOstart field and the SOend field follow, the SOstartfield and the SOend field may indicate information different from theinformation indicating the NACK_SN when there is no NACK_RANGE. That is,the SOstart field is information indicating whether in the RLC PDUhaving a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU and is segmented to the end, and theSOend field is information indicating whether in the RLC PDU having aserial number which is NACK_SN+NACK_RANGE, a segment starts from anylocation of an original RLC PDU and is segmented up to any location. Theinformation indicated by these fields is defined and promised, andconversely, may be defined as follows. That is, the SOend field isinformation indicating whether in the RLC PDU having a serial numberwhich is NACK_SN−1, a segment starts from any location of an originalRLC PDU and is segmented to the end, and the SOstart field isinformation indicating whether in the RLC PDU having a serial numberwhich is NACK_SN+NACK_RANGE, a segment starts from any location of anoriginal RLC PDU and is segmented up to any location. In addition,depending on the definition, the SOstart field may be informationindicating whether in the RLC PDU having a serial number which is theNACK_SN−1 or the NACK SN, a segment starts from any location of anoriginal RLC PDU and is segmented to the end, and the SOend field may beinformation indicating whether in the RLC PDU having the serial numberwhich is the NACK_SN+NACK_RANGE or the NACK_SN+NACK_RANGE+1, a segmentstarts from any location of an original RLC PDU and is segmented up toany location.

(When E3 field is 0)

-   -   The SOstart field indicates a head location of the part when        indicating a part of the NACK_SN. When the head location is        indicated, it may be indicated by units of byte. The SOstart has        a predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.    -   The SOend field indicates the tail location of the part when        indicating a part of the NACK_SN. When the tail location is        indicated, it may be indicated by units of byte. The SOend has a        predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.

(When E3 field is 1)

The SOstart field is information indicating whether in the RLC PDUhaving a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU and is segmented to the end. Dependingon the definition, the SOstart field is information indicating whetherin the RLC PDU having a serial number which is NACK SN, a segment startsfrom any location of an original RLC PDU and is segmented to the end.When the segmented location is indicated, it may be indicated by unitsof byte. The SOstart has a predetermined length, and the predeterminedlength can be variously defined such as 15 bits, 16 bits, and 18 bits.In addition, the SOstart field defines, as a special value, a valuehaving all zero as 000 . . . 0.0000 or a value having all 1 as 111 . . .1111 to indicate that there is no missed segment in the RLC PDU having aserial number which is the NACK_SN−1 or may indicate that the segment inthe RLC PDU having a serial number which is the NACK_SN is not missedbut the complete RLC PDU is missed.

The SOend field is information indicating whether in the RLC PDU havinga serial number which is NACK_SN−1, a segment starts from the beginningof an original RLC PDU and is segmented to any location. In addition,depending on the definition, the SOend field is information indicatingwhether in the RLC PDU having a serial number which isNACK_SN+NACK_RANGE+1, a segment starts from the beginning of an originalRLC PDU and is segmented to any location. When the segmented location isindicated, it may be indicated by units of byte. The SOend has apredetermined length, and the predetermined length can be variouslydefined such as 15 bits, 16 bits, and 18 bits. In addition, the SOendfield defines, as a special value, a value having all zero as 000 . . .0.0000 or a value having all 1 as 111 . . . 1111 to indicate that thesegment in the RLC PDU having a serial number which is theNACK_SN+NACK_RANGE is not missed or the complete RLC PDU is missed orindicate that there is no segment missed in the RL PDU having a serialnumber which is NACK_SN+NACK_RANGE+1.

The E3 field indicates whether there are NACK_RANGE (number of missingRLC PDUs) fields indicating how many serial numbers above (larger) orbelow (smaller) from the serial number indicated by the NACK_SN aremissed.

TABLE 14 E3 field value Description 0 NACK_RANGE does not follow forthis NACK_SN. 1 NACK_RANGE follows for this NACK_SN.

FIGS. 2JA-2JC are diagrams illustrating a fourth method of reporting anRLC status according to the present disclosure.

FIGS. 2JA-2JC are diagrams illustrating an example of an RLC statusreport transmitted from a receiving side RLC layer apparatus to atransmitting side RLC layer apparatus according to the fourth method ofreporting an RLC status according to the present disclosure (assuming a12-bit RLC SN length, 16-bit SO start and SOend). The third method forreporting an RLC status additionally proposes and applies a method thatcan reduce the overhead over the second method for reporting an RLCstatus.

The receiving side RLC layer device stores the received RLC PDUs in thereceiving buffer and then checks the serial number to recognize theserial number of the RLC PDU missed during the transmission. If thepredetermined condition is satisfied, the receiving side RLC layerapparatus generates an RLC status report message and transmits thegenerated RLC status report message to the transmitting side RLC layerapparatus. The predetermined condition may be a case where polling isreceived from the transmitting side RLC layer device, that is, the pollbit is set to be ‘1’ in the RLC header of the received RLC PDU. The RLCstatus report message includes information on the RLC PDU receptionstate of the receiving side RLC layer apparatus, and the transmittingside RLC layer apparatus identifies the RLC PDU successfully transmittedand the RLC PDU failed to transmit, through the RLC status reportmessage. The RLC status report message may be written like 2 j-05 inFIGS. 2JA-2JC. The RLC status report message includes one ACK_SN or aset of one ACK_SN and one or more NACK_SN, E1, NACK_TYPE fields. It isindicated by the E1 field whether there are the set of NACK_SN, E1,NACK_TYPE fields. The E1 field indicates whether a set of one NACK_SNfield, the E1 field, the E2 field, and the E3 field follow, and theNACK_TYPE field is a field consisting of 2 bits and indicates whether ornot the NACK_RANGE field and the SOstart and SOend fields follow.

For example, if the NACK_TYPE field is 00, it indicates that both of theNACK_RANGE field and the SOstart and a SOend field do not follow, andthe NACK_SN indicates the missing of the individual RLC PDU.

If the NACK_TYPE field is 10, then the NACK_RANGE field does not follow,it is indicated that the SOstart and SOend fields exist, and it isindicated that the segment of the individual RLC PDU corresponding tothe NACK_SN is missed. In this case, the SOstart and the SOend indicatewhich part of the individual RLC PDU is missed and the start part(SOstart) and the last part (SOend) of the segment is indicated by unitsof byte.

If the NACK_TYPE field is 01, the NACK_RANGE field follows, it isindicated that there are no SOstart and SOend fields, and it isindicated that the regions for the plurality of RLC PDUs consecutivefrom the NACK_SN are missed at once. In this case, the NACK_RANGE fieldis a field indicating how many the RLC PDUs are consecutively missedfrom the NACK_SN. The NACK_RANGE (the number of consecutive missing RLCPDUs) field is a field indicating how many serial numbers above (havinglarger serial number) or below (having smaller serial number) from theserial number indicated by the NACK_SN are missed.

If the NACK_TYPE field is 11, the NACK_RANGE field follows, it isindicated that there are the SOstart and SOend fields, it is indicatedthat the regions for the plurality of RLC PDUs consecutive from theNACK_SN are missed at once, and it is indicated that segments which areahead or follow are missed. In this case, it can be promised that if theNACK_TYPE field indicates that the SOstart field and the SOend fieldfollow and the NACK_RANGE field exists, the NACK_RANGE field followsjust after the NACK_SN and the SO field and the SOend field followthereafter. In this case, the SOstart field and the SOend field indicatethe segment information on the head part and the tail part of theNACK_RANGE when indicating that the NACK_RANGE field follows. That is,if the E3 field indicates that the NACK_RANGE field follows and the E2field indicates that the SOstart field and the SOend field follow, theSOstart field and the SOend field may indicate information differentfrom the information indicating the NACK_SN when there is no NACK_RANGE.That is, the SOstart field is information indicating whether in the RLCPDU having a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU and is segmented to the end, and theSOend field is information indicating whether in the RLC PDU having aserial number which is NACK_SN+NACK_RANGE, a segment starts from anylocation of an original RLC PDU and is segmented up to any location. Theinformation indicated by these fields is defined and promised, andconversely, may be defined as follows. In this case, the SOend field isinformation indicating whether in the RLC PDU having a serial numberwhich is NACK_SN−1, a segment starts from any location of an originalRLC PDU and is segmented to the end, and the SOstart field isinformation indicating whether in the RLC PDU having a serial numberwhich is NACK_SN+NACK_RANGE, a segment starts from any location of anoriginal RLC PDU and is segmented up to any location.

The ACK_SN field may include the serial number sequent to the highestsequence number among the serial numbers of RLC PDUs that havesuccessfully received so far and the NACK_SN may include the serialnumber that has not successfully received so far. When a plurality ofconsecutive RLC PDUs are missed, the highest sequence number that hasnot been received so far or the lowest serial number that has not beenreceived so far can be included in the NACK_SN in order to use NACK_SNtogether with the NACK_RANGE field, and the N field may include thenumber of missed serial numbers. The NACK_SN and NACK_RANGE fields maybe defined and applied by various other methods to indicate a number ofRLC PDUs that have been missed consecutively.

The missing of RLC PDUs can occur in a variety of ways.

First, individual RLC PDUs may be missed. That is, it may be necessaryto indicate the serial number of the missed independent RLC PDU (2j-05). The individual RLC PDUs indicate the RLC serial number of theindividual RLC PDU as the NACK_SN like 2 j-05, and set E1 to 1 toindicate another missed packet behind. Since there is no need toindicate the segment and indicate the regions for the plurality ofmissed RLC PDUs, the NACK_TYPE field may be set to be 00 to indicatethat the individual RLC PDU is missed like 2 j-05.

Second, segments of individual RLC PDUs may be missed. That is, it maybe necessary to indicate the serial number of the missed independent RLCPDU segment (2 j-10). In this case, the segments of the RLC PDUs mayindividually indicate the RLC serial numbers of the individual RLC PDUsas the NACK_SN like 2 j-10, and the NACK_TYPE field may set to be 10 toindicate the segment to indicate that the SOstart field and the SOendfield follow, indicate that there is no NACK_RANGE field, and use theSOstart Field and the SOend field to indicate the segment location ofthe corresponding RLC PDU. That is, it may be indicated whether thesegment of the individual RLC PDU is missed like 2 j-10.

Third, a number of consecutive RLC PDUs may be missed at once. That is,it may be necessary to indicate a number of consecutive RLC PDUs at once(2 j-15). A number of consecutive RLC PDUs indicate, by the NACK_SN, RLCserial numbers of an individual RLC PDU corresponding to the lowestserial number or the highest serial number like 2 j-15, and in order toindicate the regions for a number of RLC PDUs consecutively missed, theNACK_TYPE field may be set to be 1 to indicate that the NACK_RANGE fieldfollows, and indicate that there are no the SOstart field and the SOendfield to indicate the regions for the corresponding consecutive RLC PDUsusing the NACK_RANGE field. In this case, the NACK_RANGE field mayindicate how many the consecutive NACK_SNs have been missed. To indicateanother missed packet behind, the E1 may be set to be 1, indicating thatthe plurality of RLC PDUs consecutively missed like 2 j-15 are missed.

Fourth, the last segment of one RLC PDU, a number of RLC PDUsconsecutive thereafter, and a first segment of one RLC PDUs consecutivethereafter may be missed at once (2 j-20-1). The last segment of one RLCPDU and a number of RLC PDUs consecutive thereafter and the firstsegment of one RLC PDU consecutive thereafter may be indicated bysetting the NACK_TYPE field to be 11 and using the NACK_RANGE field, theSOstart field, and the SOend field together like 2 j-20. That is, theSOstart field may indicate whether in the RLC PDU having a serial numberwhich is NACK_SN−1, a segment starts from any location of an originalRLC PDU and is segmented to the end, and the SOend field may indicatewhether in the RLC PDU having a serial number which isNACK_SN+NACK_RANGE, a segment starts from any location of an originalRLC PDU and is segmented up to any location. Accordingly, the lastsegment of one RLC PDU, a number of subsequent consecutive RLC PDUs, andthe first segment of one of subsequent consecutive RLC PDUs indicate thefirst and last segments in the same manner as 2 j-10 and a number ofconsecutive RLC PDUs are indicated in the same manner as 2 j-15, whichmay be reported to the transmitting end.

Fifth, the last segment of one RLC PDU and a number of RLC PDUsconsecutive thereafter may be missed at once (2 j-20-2). The lastsegment of one RLC PDU and a number of RLC PDUs consecutive thereafterand the first segment of one RLC PDU consecutive thereafter may beindicated by setting the NACK_TYPE field to be 11 and using theNACK_RANGE field, the SOstart field, and the SOend field together like 2j-20. That is, the SOstart field may indicate whether in the RLC PDUhaving a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU, and the SOend field may define, as aspecial value, a value having all zero as 000 . . . 0.0000 or a valuehaving all 1 as 111 . . . 1111 to indicate that a segment of the RLC PDUhaving a serial number which is the NACK_SN+NACK_RANGE is not missed butthe complete RLC PDU is missed. Accordingly, the last segment of one RLCPDU and a number of RLC PDUs consecutive thereafter indicate the firstsegment in the same manner as 2 j-10 and a number of consecutive RLCPDUs are indicated in the same manner as 2 j-15, thereby more reducingthe overhead than the case of the reporting.

Sixth, a number of consecutive RLC PDUs and the first segment of anumber of RLC PDUs consecutive thereafter may be missed at once (2j-20-3). In this case, a number of consecutive RLC PDUs and a firstsegment of one RLC PDU consecutive may be indicated by setting theNACK_TYPE field to be 11 and using the NACK_RANGE field, the SOstartfield, and the SOend field together like 2 j-20. That is, the SOstartfield defines, as a special value, a value having all zero as 000 . . .0.0000 or a value having all 1 as 111 . . . 1111 to indicate that thereis no missed segment in the RLC PDU having a serial number which is theNACK_SN−1, and the SOend field may indicate whether in the RLC PDUhaving a serial number which is NACK_SN+NACK_RANGE, a segment startsfrom any location of an original RLC PDU and is segmented up to anylocation. Therefore, a number of consecutive RLC PDUs and a firstsegment of one RLC PDU consecutive thereafter indicate the last segmentin the same manner as 2 j-10 and a number of consecutive RLC PDUs areindicated in the same manner as 2 j-15, thereby more reducing theoverhead than the case of the reporting.

In order to apply the fourth method for reporting an RLC statusdescribed above, a format such as 2 j-01 may be used. In order tofacilitate processing in units of bytes, a reservation field such as 2j-02 is used or added so that the RLC status report format can beuniformly generated in units of bytes. Although the length of the RLCserial number and the length of the SOstart and the SOend are set to bedifferent lengths, the RLC status report format may be configured inunits of byte by setting (using and adding) the reserved field. That is,when the RLC status report is transmitted, the transmitting end RLClayer generates the RLC status report in units of byte, and thereceiving end may quickly read and analyze the RLC status report inunits of byte.

When the RLC status report is performed at the receiving end, if thetransmission resources are insufficient, it may not include all thereport information to be indicated as 2 j-05, 2 j-10, and 2 j-15.Therefore, if the transmission resources are insufficient, a method ofindicating a larger number of missed RLC PDUs with the same transmissionresource should be used first to perform a report. That is, if the 2j-15 method may be applied to the RLC PDUs that should be reported to bemissed, the 2 j-15 method is firstly applied to perform the report,followed by the 2 j-05 method, and then the 2 j-10 method can be appliedto perform the report. Also, if there are insufficient resources toreport 2 j-20, the reporting may be made by the 2 j-15 method, exceptthe SOstart field and the SOend field. In other words, if the resourcesare insufficient, the 2 j-15 method is preferentially applied to performthe reporting, and the 2 j-05 method may be considered, and theremaining methods may be considered.

The RLC layer apparatus transmits the RLC PDU with the serial number,and checks whether the transmitted RLC PDU succeeds based on the RLCstatus report message and retransmits the RLC PDU, thereby ensuringreliable transmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of informationlargely.

-   -   Identify RLC PDU failing to transmit    -   Identify RLC PDU failing to transmit

The transmitting side RLC layer apparatus is recognized which RLC PDU toretransmit in the future by identifying the RLC PDU failing to transmit,and it determines which RLC PDU or PDCP SDU of RLC PDUs or PDCP SDUsstored in the retransmission buffer and the transmission buffer isdiscarded.

The fields applied to the fourth method of reporting an RLC statusaccording to the present disclosure are as follows.

-   -   The D/C field has a length of 1 bit and indicates whether the        RLC PDU is an RLC data PDU or an RLC control PDU. (Table 1-16).

TABLE 15 D/C field value Description 0 Control PDU 1 Data PDU

-   -   The CPT field has a length of 3 bit and indicates a kind of RLC        control PDU. (Table 1-9).

TABLE 16 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

-   -   ACK_SN indicates the next serial number of the RLC PDU that has        not yet been received and a serial number that is not reported        as missed in the RLC status report. Upon receiving the RLC        status report at the transmitting end, it is determined that the        serial number indicated by the ACK_SN is not included, the        serial numbers indicated by the NACK_SN are not included, the        serial number included in the range indicated by the NACK_SN and        the NACK_RANGE field are not included, and the serial number        smaller than the ACK_SN has been received successfully (when the        NACK_SN is indicated together with the SOstart and the SOend, it        is determined that the SOstart and the SOend successfully        receive only a part other than the part indicated by the        NACK_SN). The ACK_SN has a predetermined length, and the        predetermined length can be variously defined such as 12 bits,        16 bits, and 18 bits.    -   The E1 field has a length of 1 bit and indicates whether or not        the NACK_SN, the E1 field, the E2 field, and the E3 field        follow.

TABLE 17 E1 field value Description 0 A set of NACK_SN, E1, E2, and E3does not follow. 1 A set of NACK_SN, E1, E2, and E3 follows.

The NACK_SN may include the serial number that has not received so far.When a plurality of consecutive RLC PDUs are missed, the highestsequence number that has not been received so far or the lowest serialnumber that has not been received so far can be included in the NACK_SNin order to use NACK_SN together with the NACK_RANGE field, and the Nfield may include the number of missed serial numbers. The NACK_SN andNACK_RANGE fields may be defined and applied by various other methods toindicate a number of RLC PDUs that have been missed consecutively. TheNACK_SN has a predetermined length, and the predetermined length can bevariously defined such as 12 bits, 16 bits, or 18 bits.

The NACK_RANGE field is a field indicating how many serial numbers above(having larger serial number) or below (having smaller serial number)from the serial number indicated by the NACK_SN are missed.

The NACK_TYPE field is a field which has a length of 2 bits andindicates whether the SOstart and SOend and the NACK_RANGE fieldsfollow. If it is indicated that the SOstart and SOend and the NACK_RANGEfields may exist, it may be promised that if the NACK_SN is followed bythe NACK_RANGE, followed by the SOstart and SOend.

TABLE 18 NACK_TY PE field value Description 00 A set of SOstart, SOend,and NACK_RANGE does not follow for this NACK_SN. 10 Only SOstart andSOend follow for this NACK_SN. 01 Only NACK_RANGE follow for thisNACK_SN. 11 A set of SOstart, SOend, and NACK_RANGE follow for thisNACK_SN.

The NACK_TYPE field is a field consisting of a 2-bit field and indicateswhether or not the NACK_RANGE field and the SOstart and SOend fieldsfollow.

For example, if the NACK_TYPE field is 00, it indicates that both of theNACK_RANGE field and the SOstart and a SOend field do not follow, andthe NACK_SN indicates the missing of the individual RLC PDU.

If the NACK_TYPE field is 10, then the NACK_RANGE field does not follow,it is indicated that the SOstart and SOend fields exist, and it isindicated that the segment of the individual RLC PDU corresponding tothe NACK_SN is missed. In this case, the SOstart and the SOend indicatewhich part of the individual RLC PDU is missed and the start part(SOstart) and the last part (SOend) of the segment is indicated by unitsof byte.

If the NACK_TYPE field is 01, the NACK_RANGE field follows, it isindicated that there are no SOstart and SOend fields, and it isindicated that the regions for the plurality of RLC PDUs consecutivefrom the NACK_SN are missed at once. In this case, the NACK_RANGE fieldis a field indicating how many the RLC PDUs are consecutively missedfrom the NACK_SN. The NACK_RANGE (the number of consecutive missing RLCPDUs) field is a field indicating how many serial numbers above (havinglarger serial number) or below (having smaller serial number) from theserial number indicated by the NACK_SN are missed.

If the NACK_TYPE field is 11, the NACK_RANGE field follows, it isindicated that there are the SOstart and SOend fields, it is indicatedthat the regions for the plurality of RLC PDUs consecutive from theNACK_SN are missed at once, and it is indicated that segments which areahead or follow are missed. In this case, it can be promised that if theNACK_TYPE field indicates that the SOstart field and the SOend fieldfollow and the NACK_RANGE field exists, the NACK_RANGE field followsjust after the NACK_SN and the SO field and the SOend field followthereafter. In this case, the SOstart field and the SOend field indicatethe segment information on the head part and the tail part of theNACK_RANGE when indicating that the NACK_RANGE field follows. That is,if the E3 field indicates that the NACK_RANGE field follows and the E2field indicates that the SOstart field and the SOend field follow, theSOstart field and the SOend field may indicate information differentfrom the information indicating the NACK_SN when there is no NACK_RANGE.That is, the SOstart field is information indicating whether in the RLCPDU having a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU and is segmented to the end, and theSOend field is information indicating whether in the RLC PDU having aserial number which is NACK_SN+NACK_RANGE, a segment starts from anylocation of an original RLC PDU and is segmented up to any location. Theinformation indicated by these fields is defined and promised, andconversely, may be defined as follows. That is, the SOend field isinformation indicating whether in the RLC PDU having a serial numberwhich is NACK_SN−1, a segment starts from any location of an originalRLC PDU and is segmented to the end, and the SOstart field isinformation indicating whether in the RLC PDU having a serial numberwhich is NACK_SN+NACK_RANGE, a segment starts from any location of anoriginal RLC PDU and is segmented up to any location.

(When NACK_TYPE field is 10)

-   -   The SOstart field indicates a head location of the part when        indicating a part of the NACK_SN. When the head location is        indicated, it may be indicated by units of byte. The SOstart has        a predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.    -   The SOend field indicates the tail location of the part when        indicating a part of the NACK_SN. When the tail location is        indicated, it may be indicated by units of byte. The SOend has a        predetermined length, and the predetermined length can be        variously defined such as 15 bits, 16 bits, and 18 bits.

(When NACK_TYPE field is 11)

The SOstart field is information indicating whether in the RLC PDUhaving a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU and is segmented to the end. Dependingon the definition, the SOstart field is information indicating whetherin the RLC PDU having a serial number which is NACK SN, a segment startsfrom any location of an original RLC PDU and is segmented to the end.When the segmented location is indicated, it may be indicated by unitsof byte. The SOstart has a predetermined length, and the predeterminedlength can be variously defined such as 15 bits, 16 bits, and 18 bits.In addition, the SOstart field defines, as a special value, a valuehaving all zero as 000 . . . 0.0000 or a value having all 1 as 111 . . .1111 to indicate that there is no missed segment in the RLC PDU having aserial number which is the NACK_SN−1 or may indicate that the segment inthe RLC PDU having a serial number which is the NACK_SN is not missedbut the complete RLC PDU is missed.

-   -   The SOend field is information indicating whether in the RLC PDU        having a serial number which is NACK_SN−1, a segment starts from        the beginning of an original RLC PDU and is segmented to any        location. In addition, depending on the definition, the SOend        field is information indicating whether in the RLC PDU having a        serial number which is NACK_SN+NACK_RANGE+1, a segment starts        from the beginning of an original RLC PDU and is segmented to        any location. When the segmented location is indicated, it may        be indicated by units of byte. The SOend has a predetermined        length, and the predetermined length can be variously defined        such as 15 bits, 16 bits, and 18 bits. In addition, the SOend        field defines, as a special value, a value having all zero as        000 . . . 0.0000 or a value having all 1 as 111 . . . 1111 to        indicate that the segment in the RLC PDU having a serial number        which is the NACK_SN+NACK_RANGE is not missed or the complete        RLC PDU is missed or indicate that there is no segment missed in        the RL PDU having a serial number which is NACK_SN+NACK_RANGE+1.

FIG. 2K is a diagram illustrating an operation of a terminal to whichthe embodiments of the present disclosure are applied.

In FIG. 2K, the operation of the terminal to which the second method forreporting an RLC state according to the present disclosure is applied isas follows.

The terminal identifies the missed RLC PDU information at the time ofattempting to configure the RLC status report (2 k-05).

If the missed RLC PDU information satisfies the first condition, thefirst operation may be performed. (2 k-10)

If the missed RLC PDU information satisfies the second condition, thesecond operation may be performed. (2 k-15)

If the missed RLC PDU information satisfies the third condition, thethird operation may be performed. (2 k-20)

If the missed RLC PDU information satisfies the fourth condition, thefourth operation may be performed. (2 k-25)

If the missed RLC PDU information satisfies the fifth condition, thefifth operation may be performed. (2 k-30)

If the missed RLC PDU information satisfies the sixth condition, thesixth operation may be performed. (2 k-35)

In this case, the first condition is the case in which the individualRLC PDUs are missed. (2 h-05). That is, the first operation mayindicate, by the NACK_SN, the RLC serial numbers of the individual RLCPDUs like 2 h-05 in order to indicate the serial numbers of theindependently missed RLC PDUs, set the E1 to be 1 in order to indicateanother missed packet behind, set the E2 to be 0 since there is no needto indicate the segment, and set the E3 to be 0 since there is no needto indicate the regions for the plurality of missed RLC PDUs, therebyindicating that the individual RLC PDU is missed like 2 h-05.

In this case, the second condition is the case in which the individualRLC PDUs are missed. (2 h-10). That is, the second operation mayindicate, by the NACK_SN, the RLC serial numbers of the individual RLCPDUs like 2 h-10 in order to indicate the missed independent RLC PDUsegments, set the E2 to be 1 to the segment to, indicate that there arethe SOstart field and the SOend field behind, and indicate the segmentlocation of the corresponding RLC PDU using the SOstart field and theSOend field. In order to indicate another missed packet behind, E1 isset to be 1, and since the regions for the plurality of missed RLC PDUsare not indicated, E3 may be set to be 0 to indicate the segments of theindividual RLC PDUs are missed like 2 h-10.

In this case, the third condition is the case in which a number ofconsecutive RLC PDUs are missed at once. (2 h-10). That is, the thirdoperation may indicate, by the NACK_SN, RLC serial numbers of anindividual RLC PDU corresponding to the lowest serial number or thehighest serial number like 2 h-15 in order to indicate a number ofconsecutive RLC PDUs at once, set the E3 to be 1 to in order to indicateregions for a number of RLC PDUs consecutively missed to indicate thatthe NACK_RANGE field follows, and indicate the regions for thecorresponding consecutive RLC PDUs using the NACK_RANGE field. In thiscase, the NACK_RANGE field may indicate how many the consecutiveNACK_SNs have been missed. Then, to indicate another missed packet, theE1 may be set to be 1. Since there is no need to indicate the segment,the E2 may be set to be 0 to indicate that the plurality of RLC PDUs aremissed consecutively like 2 h-15.

In this case, the fourth operation is the case in which the last segmentof one RLC PDU, a number of RLC PDUs consecutive thereafter, and a firstsegment of one RLC PDU consecutive thereafter are missed at once (2h-20-1).

That is, in the fourth operation, the last segment of one RLC PDU, anumber of RLC PDUs consecutive thereafter, and the first segment of oneRLC PDU consecutive thereafter indicate the first and last segments inthe same manner as 2 h-10 and a number of consecutive RLC PDUs areindicated in the same manner as 2 h-15, which may be reported to thetransmitting end.

In this case, the fifth operation is the case in which the last segmentof one RLC PDU and a number of RLC PDUs consecutive thereafter may bemissed at once (2 h-20-2). That is, in the fifth operation, the lastsegment of one RLC PDU and a number of RLC PDUs consecutive thereafterindicate the first segment in the same manner as 2 h-10 and a number ofconsecutive RLC PDUs are indicated in the same manner as 2 h-15, whichmay be reported to the transmitting end.

In this case, the sixth case is the case in which a number ofconsecutive RLC PDUs and the first segment of a number of RLC PDUsconsecutive thereafter may be missed at once (2 h-20-3). That is, in thesixth operation, a number of consecutive RLC PDUs and the first segmentof one RLC PDU consecutive thereafter indicate the last segment in thesame manner as 2 h-10 and a number of consecutive RLC PDUs are indicatedin the same manner as 2 h-15, which may be reported to the transmittingend.

After one of the six conditions is satisfied and thus one operation isperformed, the terminal again proceeds to step 2 k-05 to again identifythe six conditions to additionally report another missed RLC PDU andcontinuously performs the operation corresponding thereto to report allthe missed RLC PDUs. The above operation may be repeatedly performeduntil the RLC status report for reporting the missed RLC PDUs iscompleted or the RLC status report is filled by the size of theallocated transmission resources.

In FIG. 2K, the operation of the terminal to which the third method forreporting an RLC state according to the present disclosure is applied isas follows.

The terminal identifies the missed RLC PDU information at the time ofattempting to configure the RLC status report (2 k-05).

If the missed RLC PDU information satisfies the first condition, thefirst operation may be performed. (2 k-10)

If the missed RLC PDU information satisfies the second condition, thesecond operation may be performed. (2 k-15)

If the missed RLC PDU information satisfies the third condition, thethird operation may be performed. (2 k-20)

If the missed RLC PDU information satisfies the fourth condition, thefourth operation may be performed. (2 k-25)

If the missed RLC PDU information satisfies the fifth condition, thefifth operation may be performed. (2 k-30)

If the missed RLC PDU information satisfies the sixth condition, thesixth operation may be performed. (2 k-35)

In this case, the first condition is the case in which the individualRLC PDUs are missed. (2 i-05). That is, the first operation mayindicate, by the NACK_SN, the RLC serial numbers of the individual RLCPDUs like 2 i-05, set E1 to be 1 in order to indicate another missedpacket behind, set E2 to be 0 since there is no need to indicate thesegment, and set E3 to be 0 since there is no need to indicate theregions for the plurality of missed RLC PDUs, thereby indicating thatthe individual RLC PDU is missed like 2 i-05.

In this case, the second operation is the case in which the segments ofthe individual RLC PDUs are missed. (2 i-10). That is, the secondoperation may indicate, by the NACK_SN, the serial numbers of the RLCserial numbers of the individual RLC PDUs like 2 i-10, set E2 to be 1 toindicate the segment to indicate that there are the SOstart field andthe SOend field behind, and indicate the segment location of thecorresponding RLC PDU using the SOstart field and the SOend field. Inorder to indicate another missed packet behind, E1 is set to be 1. Sincethe regions for the plurality of missed RLC PDUs is not indicated, E3may be set to be 0 to indicate the segments of the individual RLC PDUsare missed like 2 i-10.

In this case, the third condition is the case in which a number ofconsecutive RLC PDUs are missed. (2 i-15). That is, the third operationmay indicate, by the NACK_SN, the RLC serial numbers of an individualRLC PDU corresponding to the lowest serial number or the highest serialnumber like 2 i-15, set E3 to be 1 to indicate the regions for a numberof RLC PDUs consecutively missed to indicate that the NACK_RANGE fieldfollows, and indicate the regions for the corresponding consecutive RLCPDUs using the NACK_RANGE field. In this case, the NACK_RANGE field mayindicate how many the consecutive NACK_SNs have been missed. Then, toindicate another missed packet, E1 may be set to be 1. Since there is noneed to indicate the segment, E2 may be set to be 0 to indicate that theplurality of RLC PDUs are missed consecutively like 2 i-15.

In this case, the fourth condition is the case in which the last segmentof one RLC PDU, a number of RLC PDUs consecutive thereafter, and thefirst segment of one RLC PDU consecutive thereafter are missed at once.(2 i-20-1). That is, the fourth operation may indicate the missing ofthe last segment of one RLC PDU, a number of RLC PDUs consecutivethereafter, and the first segment of one RLC PDU consecutive thereafterby using the NACK_RANGE field and the SOstart field and the SOend fieldtogether like 2 i-20. That is, the SOstart field may indicate whether inthe RLC PDU having a serial number which is NACK_SN−1, a segment startsfrom any location of an original RLC PDU and is segmented to the end,and the SOend field may indicate whether in the RLC PDU having a serialnumber which is NACK_SN+NACK_RANGE, a segment starts from any locationof an original RLC PDU and is segmented up to any location. Accordingly,the last segment of one RLC PDU, a number of subsequent consecutive RLCPDUs, and the first segment of one of subsequent consecutive RLC PDUsindicate the first and last segments in the same manner as 2 i-10 and anumber of consecutive RLC PDUs are indicated in the same manner as 2i-15, which may be reported to the transmitting end.

In this case, the fifth condition is the case in which the segment ofone RLC PDU and a large number of RLC PDUs consecutive thereafter aremissed at once (2 i-20-2). That is, the fifth operation may indicate themission of the last segment of one RLC PDU and a number of RLC PDUsconsecutive thereafter by using the NACK_RANGE field and the SOstartfield and the SOend field like 2 i-20. That is, the SOstart field mayindicate whether in the RLC PDU having a serial number which isNACK_SN−1, a segment starts from any location of an original RLC PDU,and the SOend field may define, as a special value, a value having allzero as 000 . . . 0.0000 or a value having all 1 as 111 . . . 1111 toindicate that a segment of the RLC PDU having a serial number which isthe NACK_SN+NACK_RANGE is not missed but the complete RLC PDU is missed.Accordingly, the last segment of one RLC PDU and a number of RLC PDUsconsecutive thereafter indicate the first segment in the same manner as2 i-10 and a number of consecutive RLC PDUs are indicated in the samemanner as 2 i-15, thereby more reducing the overhead than the case ofthe reporting.

In this case, the sixth condition is the case in which a number ofconsecutive RLC PDUs and the first segment of one RLC PDU consecutivethereafter are missed at once (2 i-20-3). That is, the sixth operationmay indicate the missing of a number of consecutive RLC PDUs and thefirst segment of one RLC PDU consecutive thereafter by using theNACK_RANGE field and the SOstart and the SOend field like 2 i-20. Thatis, the SOstart field defines, as a special value, a value having allzero as 000 . . . 0.0000 or a value having all 1 as 111 . . . 1111 toindicate that there is no missed segment in the RLC PDU having a serialnumber which is the NACK_SN−1, and the SOend field may indicate whetherin the RLC PDU having a serial number which is NACK_SN+NACK_RANGE, asegment starts from any location of an original RLC PDU and is segmentedup to any location. Therefore, a number of consecutive RLC PDUs and thefirst segment of one RLC PDU consecutive thereafter indicate the lastsegment in the same manner as 2 i-10 and a number of consecutive RLCPDUs are indicated in the same manner as 2 i-15, thereby more reducingthe overhead than the case of the reporting.

After one of the six conditions is satisfied and thus one operation isperformed, the terminal again proceeds to step 2 k-05 to again identifythe six conditions to additionally report another missed RLC PDU andcontinuously performs the operation corresponding thereto to report allthe missed RLC PDUs. The above operation may be repeatedly performeduntil the RLC status report for reporting the missed RLC PDUs iscompleted or the RLC status report is filled by the size of theallocated transmission resources.

In FIG. 2K, the operation of the terminal to which the fourth method forreporting an RLC state according to the present disclosure is applied isas follows.

The terminal identifies the missed RLC PDU information at the time ofattempting to configure the RLC status report (2 k-05).

If the missed RLC PDU information satisfies the first condition, thefirst operation may be performed. (2 k-10)

If the missed RLC PDU information satisfies the second condition, thesecond operation may be performed. (2 k-15)

If the missed RLC PDU information satisfies the third condition, thethird operation may be performed. (2 k-20)

If the missed RLC PDU information satisfies the fourth condition, thefourth operation may be performed. (2 k-25)

If the missed RLC PDU information satisfies the fifth condition, thefifth operation may be performed. (2 k-30)

If the missed RLC PDU information satisfies the sixth condition, thesixth operation may be performed. (2 k-35)

In this case, the first condition is the case in which the individualRLC PDUs are missed. (2 j-05). That is, the first operation mayindicate, by the NACK_SN, the RLC serial numbers of the individual RLCPDUs like 2 i-05, set E1 to be 1 in order to indicate another missedpacket behind, need not indicate the segment, and set the NACK_TYPEfield to be 00 since there is no need to indicate the segment, therebyindicating that the individual RLC PDU is missed like 2 j-05.

In this case, the second operation is the case in which the segments ofthe individual RLC PDUs are missed. (2 j-10). That is, the secondoperation may indicate, by the NACK_SN, the serial numbers of the RLCserial numbers of the individual RLC PDUs like 2 j-10, set the NACK_TYPEfield to be 10 to indicate the segment to indicate that there are theSOstart field and the SOend field behind, indicate that there is noNACK_FIELD field, and indicate the segment location of the correspondingRLC PDU using the SOstart field and the SOend field. That is, it may beindicated whether the segment of the individual RLC PDU is missed like 2j-10.

In this case, the third condition is the case in which a number ofconsecutive RLC PDUs are missed. (2 j-15). That is, the third operationmay indicate, by the NACK_SN, the RLC serial numbers of an individualRLC PDU corresponding to the lowest serial number or the highest serialnumber like 2 ji-15, set the NACK_TYPE field to be 01 to indicate theregions for a number of RLC PDUs consecutively missed to indicate thatthe NACK_RANGE field follows, and indicate that there are no SOstartfield and SOend field to indicate the regions for the correspondingconsecutive RLC PDUs using the NACK_RANGE field. In this case, theNACK_RANGE field may indicate how many the consecutive NACK_SNs havebeen missed. To indicate another missed packet behind, the E1 may be setto be 1, indicating that the plurality of RLC PDUs consecutively missedlike 2 j-15 are missed.

In this case, the fourth condition is the case in which the last segmentof one RLC PDU, a number of RLC PDUs consecutive thereafter, and thefirst segment of one RLC PDU consecutive thereafter are missed at once.(2 j-20-1). That is, the fourth operation may indicate the missing ofthe last segment of one RLC PDU, a number of RLC PDUs consecutivethereafter, and the first segment of one RLC PDU consecutive thereafterby setting the NACK_TYPE field to be 11 and using the NACK_RANGE fieldand the SOstart field and the SOend field together like 2 j-20. That is,the SOstart field may indicate whether in the RLC PDU having a serialnumber which is NACK_SN−1, a segment starts from any location of anoriginal RLC PDU and is segmented to the end, and the SOend field mayindicate whether in the RLC PDU having a serial number which isNACK_SN+NACK_RANGE, a segment starts from any location of an originalRLC PDU and is segmented up to any location. Accordingly, the lastsegment of one RLC PDU, a number of subsequent consecutive RLC PDUs, andthe first segment of one of subsequent consecutive RLC PDUs indicate thefirst and last segments in the same manner as 2 j-10 and a number ofconsecutive RLC PDUs are indicated in the same manner as 2 j-15, whichmay be reported to the transmitting end.

In this case, the fifth condition is the case in which the segment ofone RLC PDU and a large number of RLC PDUs consecutive thereafter aremissed at once (2 j-20-2). That is, the fifth operation may indicate themission of the last segment of one RLC PDU and a number of RLC PDUsconsecutive thereafter by setting the NACK_TYPE field to be 11 and usingthe NACK_RANGE field and the SOstart field and the SOend field like 2j-20. That is, the SOstart field may indicate whether in the RLC PDUhaving a serial number which is NACK_SN−1, a segment starts from anylocation of an original RLC PDU, and the SOend field may define, as aspecial value, a value having all zero as 000 . . . 0.0000 or a valuehaving all 1 as 111 . . . 1111 to indicate that a segment of the RLC PDUhaving a serial number which is the NACK_SN+NACK_RANGE is not missed butthe complete RLC PDU is missed. Accordingly, the last segment of one RLCPDU and a number of RLC PDUs consecutive thereafter indicate the firstsegment in the same manner as 2 j-10 and a number of consecutive RLCPDUs are indicated in the same manner as 2 j-15, thereby more reducingthe overhead than the case of the reporting.

In this case, the sixth condition is the case in which a number ofconsecutive RLC PDUs and the first segment of one RLC PDU consecutivethereafter are missed at once (2 j-20-3). That is, the sixth operationmay indicate the missing of a number of consecutive RLC PDUs and thefirst segment of one RLC PDU consecutive thereafter by setting theNACK_TYPE field to be 11 and using the NACK_RANGE field and the SOstartand the SOend field like 2 j-20. That is, the SOstart field defines, asa special value, a value having all zero as 000 . . . 0.0000 or a valuehaving all 1 as 111 . . . 1111 to indicate that there is no missedsegment in the RLC PDU having a serial number which is the NACK_SN−1,and the SOend field may indicate whether in the RLC PDU having a serialnumber which is NACK_SN+NACK_RANGE, a segment starts from any locationof an original RLC PDU and is segmented up to any location. Therefore, anumber of consecutive RLC PDUs and a first segment of one RLC PDUconsecutive thereafter indicate the last segment in the same manner as 2j-10 and a number of consecutive RLC PDUs are indicated in the samemanner as 2 j-15, thereby more reducing the overhead than the case ofthe reporting.

After one of the six conditions is satisfied and thus one operation isperformed, the terminal again proceeds to step 2 k-05 to again identifythe six conditions to additionally report another missed RLC PDU andcontinuously performs the operation corresponding thereto to report allthe missed RLC PDUs. The above operation may be repeatedly performeduntil the RLC status report for reporting the missed RLC PDUs iscompleted or the RLC status report is filled by the size of theallocated transmission resources.

FIG. 2L is a diagram illustrating the structure of the terminal to whichthe embodiment of the present disclosure may be applied.

Referring to FIG. 2L, the terminal includes a radio frequency (RF)processor 21-10, a baseband processor 21-20, a memory 21-30, and acontroller 21-40.

The RF processor 21-10 serves to transmit/receive a signal through aradio channel, such as band conversion and amplification of a signal.That is, the RF processor 21-10 up-converts a baseband signal providedfrom the baseband processor 21-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. Forexample, the RF processor 21-10 may include a transmitting filter, areceiving filter, an amplifier, a mixer, an oscillator, a digital toanalog converter (DAC), an analog to digital converter (ADC), or thelike. In the above figure, only one antenna is illustrated, but theterminal may include a plurality of antennas. Further, the RF processor21-10 may include the plurality of RF chains. Further, the RF processor21-10 may perform beamforming. For the beamforming, the RF processor21-10 may adjust a phase and a size of each of the signals transmittedand received through a plurality of antennas or antenna elements. Inaddition, the RF processor may perform MIMO and may receive a pluralityof layers when performing a MIMO operation. The RF processor 21-10 mayperform reception beam sweeping by appropriately configuring a pluralityof antennas or antenna elements under the control of the controller oradjust a direction and a beam width of the reception beam so that thereception beam is resonated with the transmission beam.

The baseband processor 21-20 performs a conversion function between thebaseband signal and the bit string according to a physical layerstandard of the system. For example, when data are transmitted, thebaseband processor 21-20 generates complex symbols by coding andmodulating a transmitting bit string. Further, when data are received,the baseband processor 21-20 recovers the received bit string bydemodulating and decoding the baseband signal provided from the RFprocessor 21-10. For example, according to the orthogonal frequencydivision multiplexing (OFDM) scheme, when data are transmitted, thebaseband processor 21-20 generates the complex symbols by coding andmodulating the transmitting bit string, maps the complex symbols tosub-carriers, and then performs an inverse fast Fourier transform (IFFT)operation and a cyclic prefix (CP) insertion to configure the OFDMsymbols. Further, when data are received, the baseband processor 21-20divides the baseband signal provided from the RF processor 21-10 in anOFDM symbol unit and recovers the signals mapped to the sub-carriers bya fast Fourier transform (FFT) operation and then recovers the receivingbit string by the modulation and decoding.

The baseband processor 21-20 and the RF processor 21-10 transmit andreceive a signal as described above. Therefore, the baseband processor21-20 and the RF processor 21-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. Further, at least oneof the baseband processor 21-20 and the RF processor 21-10 may include aplurality of communication modules to support a plurality of differentradio access technologies. Further, at least one of the basebandprocessor 21-20 and the RF processor 21-10 may include differentcommunication modules to process signals in different frequency bands.For example, the different wireless access technologies may include anLTE network, an NR network, and the like. Further, different frequencybands may include a super high frequency (SHF) (for example: 2.5 GHz, 5GHz) band, a millimeter wave (for example: 60 GHz) band.

The memory 21-30 stores data such as basic programs, applicationprograms, and configuration information or the like for the operation ofthe terminal. Further, the memory 21-30 provides the stored dataaccording to the request of the controller 21-40.

The controller 21-40 controls the overall operations of the terminal.For example, the controller 21-40 transmits/receives a signal throughthe baseband processor 21-20 and the RF processor 21-10. Further, thecontroller 21-40 records and reads data in and from the memory 21-30.For this purpose, the controller 21-40 may include at least oneprocessor. For example, the controller 21-40 may include a communicationprocessor (CP) performing a control for communication and an applicationprocessor (AP) controlling an upper layer such as the applicationprograms. According to the embodiment of the present disclosure, thecontroller 21-40 includes a multi-link processor 21-42 that performs theprocessing to be operated in a multi-link mode.

FIG. 2M illustrates a block configuration diagram of TRP in a wirelesscommunication system to which the embodiment of the present disclosuremay be applied.

As illustrated in FIG. 2M, the base station is configured to include anRF processor 2 m-10, a baseband processor 2 m-20, a communication unit 2m-30, a memory 2 m-40, and a controller 2 m-50.

The RF processor 2 m-10 serves to transmit/receive a signal through aradio channel, such as band conversion and amplification of a signal.That is, the RF processor 2 m-10 up-converts a baseband signal providedfrom the baseband processor 2 m-20 into an RF band signal and thentransmits the baseband signal through an antenna and down-converts theRF band signal received through the antenna into the baseband signal.For example, the RF processor 2 m-10 may include a transmitting filter,a receiving filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,etc. In the above figure, only one antenna is illustrated, but the firstaccess node may include a plurality of antennas. Further, the RFprocessor 2 m-10 may include the plurality of RF chains. Further, the RFprocessor 2 m-10 may perform the beamforming. For the beamforming, theRF processor 2 m-10 may adjust a phase and a size of each of the signalstransmitted and received through a plurality of antennas or antennaelements. The RF processor may perform a downward MIMO operation bytransmitting one or more layers.

The baseband processor 2 m-20 performs a conversion function between thebaseband signal and the bit string according to the physical layerstandard of the first radio access technology. For example, when dataare transmitted, the baseband processor 2 m-20 generates complex symbolsby coding and modulating a transmitting bit string. Further, when dataare received, the baseband processor 2 m-20 recovers the received bitstring by demodulating and decoding the baseband signal provided fromthe RF processor 2 m-10. For example, according to the OFDM scheme, whendata are transmitted, the baseband processor 2 m-20 generates thecomplex symbols by coding and modulating the transmitting bit string,maps the complex symbols to the sub-carriers, and then performs the IFFToperation and the CP insertion to configure the OFDM symbols. Further,when data are received, the baseband processor 2 m-20 divides thebaseband signal provided from the RF processor 2 m-10 in an OFDM symbolunit and recovers the signals mapped to the sub-carriers by an FFToperation and then recovers the receiving bit string by the modulationand decoding. The baseband processor 2 m-20 and the RF processor 2 m-10transmit and receive a signal as described above. Therefore, thebaseband processor 2 m-20 and the RF processor 2 m-10 may be called atransmitter, a receiver, a transceiver, a communication unit, or awireless communication unit.

The communicator 2 m-30 provides an interface for performingcommunication with other nodes within the network.

The memory 2 m-40 stores data such as basic programs, applicationprograms, and setup information for the operation of the main basestation. In particular, the memory 2 m-40 may store the information onthe bearer allocated to the accessed terminal, the measured resultsreported from the accessed terminal, etc. Further, the memory 2 m-40 maystore information that is a determination criterion on whether toprovide a multiple connection to the terminal or stop the multipleconnection to the terminal. Further, the memory 2 m-40 provides thestored data according to the request of the controller 2 m-50.

The controller 2 m-50 controls the general operations of the main basestation. For example, the controller 2 m-50 transmits/receives a signalthrough the baseband processor 2 m-20 and the RF processor 2 m-10 or thebackhaul communicator 2 m-30. Further, the controller 2 m-50 records andreads data in and from the memory 2 m-40. For this purpose, thecontroller 2 m-50 may include at least one processor. According to theembodiment of the present disclosure, the controller 2 m-50 includes amulti-link processor 2 m-52 that performs the processing to be operatedin a multi-link mode.

FIG. 3A is a diagram illustrating a structure of an LTE system to whichthe present disclosure may be applied.

As illustrated in FIG. 3A, a radio access network of an LTE system isconfigured to include next generation base stations (evolved node B,hereinafter, ENB, Node B, or base station) 3 a-05, 3 a-10, 3 a-15, and 3a-20, a mobility management entity (MME) 3 a-25, and a serving-gateway(S-GW) 3 a-30. User equipment (hereinafter, UE or terminal) 3 a-35accesses an external network through the ENBs 3 a-05 to 3 a-20 and theS-GW 3 a-30.

In FIG. 3A, the ENBs 3 a-05 to 3 a-20 correspond to the existing node Bof the UMTS system. The ENB is connected to the UE 3 a-35 through aradio channel and performs more complicated role than the existing nodeB. In the LTE system, in addition to a real-time service like a voiceover Internet protocol (VoIP) through the Internet protocol, all theuser traffics are served through a shared channel and therefore anapparatus for collecting and scheduling status information such as abuffer status, an available transmission power status, and a channelstatus of the terminals is used. Here, the eNBs 3 a-05 to 3 a-20 takecharge of the collecting and scheduling. One ENB generally controls aplurality of cells. For example, to implement a transmission rate of 100Mbps, the LTE system uses, as a radio access technology, orthogonalfrequency division multiplexing (hereinafter, OFDM) in, for example, abandwidth of 20 MHz. Further, an adaptive modulation & coding(hereinafter, referred to as AMC) determining a modulation scheme and achannel coding rate according to a channel status of the terminal isapplied. The S-GW 3 a-30 is an apparatus for providing a data bearer andgenerates or removes the data bearer according to the control of the MME3 a-25. The MME is an apparatus for performing a mobility managementfunction for the terminal and various control functions and is connectedto a plurality of base stations.

FIG. 3B is a diagram illustrating a radio protocol structure in the LTEsystem to which the present disclosure may be applied.

Referring to FIG. 3B, the radio protocol of the LTE system is configuredto include packet data convergence protocols (PDCPs) 3 b-05 and 3 b-40,radio link controls (RLCs) 3 b-10 and 3 b-35, and medium access controls(MACs) 3 b-15 and 3 b-30, respectively, in the terminal and the ENB,respectively. The packet data convergence protocols (PDCPs) 3 b-05 and 3b-40 are in charge of operations such as IP headercompression/decompression. The main functions of the PDCP are summarizedas follows.

-   -   Header compression and decompression function (Header        compression and decompression: ROHC only)    -   Transfer function of user data (Transfer of user data)    -   In-sequence delivery function (In-sequence delivery of upper        layer PDUs at PDCP re-establishment procedure for RLC AM)    -   Reordering function (For split bearers in DC (only support for        RLC AM): PDCP PDU routing for transmission and PDCP PDU        reordering for reception)    -   Duplicate detection function (Duplicate detection of lower layer        SDUs at PDCP re-establishment procedure for RLC AM)    -   Retransmission function (Retransmission of PDCP SDUs at handover        and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery        procedure, for RLC AM)    -   Ciphering and deciphering function (Ciphering and deciphering)    -   Timer-based SDU discard function (Timer-based SDU discard in        uplink)

The radio link controls (hereinafter, referred to as RLCs) 3 b-10 and 3b-35 reconfigures the PDCP packet data unit (PDU) to an appropriate sizeto perform the ARQ operation or the like. The main functions of the RLCare summarized as follows.

-   -   Data transfer function (Transfer of upper layer PDUs)    -   ARQ function (Error Correction through ARQ (only for AM data        transfer))    -   Concatenation, segmentation, reassembly functions        (Concatenation, segmentation and reassembly of RLC SDUs (only        for UM and AM data transfer))    -   Re-segmentation function (Re-segmentation of RLC data PDUs (only        for AM data transfer))    -   Reordering function (Reordering of RLC data PDUs (only for UM        and AM data transfer)    -   Duplicate detection function (Duplicate detection (only for UM        and AM data transfer))    -   Error detection function (Protocol error detection (only for AM        data transfer))    -   RLC SDU discard function (RLC SDU discard (only for UM and AM        data transfer))    -   RLC re-establishment function (RLC re-establishment)

The MACs 3 b-15 and 3 b-30 are connected to several RLC layer devicesconfigured in one terminal and perform an operation of multiplexing RLCPDUs into a MAC PDU and demultiplexing the RLC PDUs from the MAC PDU.The main functions of the MAC are summarized as follows.

-   -   Mapping function (Mapping between logical channels and transport        channels)    -   Multiplexing/demultiplexing function        (Multiplexing/demultiplexing of MAC SDUs belonging to one or        different logical channels into/from transport blocks (TB)        delivered to/from the physical layer on transport channels)    -   Scheduling information reporting function (Scheduling        information reporting)    -   HARQ function (Error correction through HARQ)    -   Priority handling function between logical channels (Priority        handling between logical channels of one UE)    -   Priority handling function between terminals (Priority handling        between UEs by means of dynamic scheduling)    -   MBMS service identification function (MBMS service        identification)    -   Transport format selection function (Transport format selection)    -   Padding function (Padding)

Physical layers 3 b-20 and 3 b-25 perform an operation of channel-codingand modulating higher layer data, making the higher layer data as anOFDM symbol and transmitting them to a radio channel, or demodulatingand channel-decoding the OFDM symbol received through the radio channeland transmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

FIG. 3C is a diagram illustrating a structure of a next generationmobile communication system to which the present disclosure may beapplied.

Referring to FIG. 3C, a radio access network of a next generation mobilecommunication system (hereinafter referred to as NR or 5G) is configuredto include a next generation base station (New radio node B, hereinafterNR gNB or NR base station) 3 c-10 and a new radio core network (NR CN) 3c-05. The user terminal (new radio user equipment, hereinafter, NR UE orUE) 3 c-15 accesses the external network through the NR gNB 3 c-10 andthe NR CN 3 c-05.

In FIG. 3C, the NR gNB 3 c-10 corresponds to an evolved node B (eNB) ofthe existing LTE system. The NR gNB is connected to the NR UE 3 c-15 viaa radio channel and may provide a service superior to the existing nodeB. In the next generation mobile communication system, since all usertraffics are served through a shared channel, an apparatus forcollecting state information such as a buffer status, an availabletransmission power state, and a channel status of the UEs to performscheduling is used. The NR gNB 3 c-10 may serve as the device. One NRgNB generally controls a plurality of cells. In order to realizehigh-speed data transmission compared with the current LTE, the NR gNBmay have an existing maximum bandwidth or more, and may be additionallyincorporated into a beam-forming technology may be applied by usingorthogonal frequency division multiplexing (hereinafter, referred to asOFDM) as a radio access technology. Further, an adaptive modulation &coding (hereinafter, referred to as AMC) determining a modulation schemeand a channel coding rate according to a channel status of the terminalis applied. The NR CN 3 c-05 may perform functions such as mobilitysupport, bearer setup, QoS setup, and the like. The NR CN is anapparatus for performing a mobility management function for the terminaland various control functions and is connected to a plurality of basestations. In addition, the next generation mobile communication systemcan interwork with the existing LTE system, and the NR CN is connectedto the MME 3 c-25 through the network interface. The MME is connected tothe eNB 3 c-30 which is the existing base station.

FIG. 3D is a diagram illustrating the radio protocol structure of thenext generation mobile communication system to which the presentdisclosure may be applied.

Referring to FIG. 3D, the radio protocol of the next generation mobilecommunication system is configured to include NR PDCPs 3 d-05 and 3d-40, NR RLCs 3 d-10 and 3 d-35, and NR MACs 3 d-15 and 3 d-30 in theterminal and the NR base station. The main functions of the NR PDCPs 3d-05 and 3 d-40 may include some of the following functions.

-   -   Header compression and decompression function (Header        compression and decompression: ROHC only)    -   Transfer function of user data (Transfer of user data)    -   In-sequence delivery function (In-sequence delivery of upper        layer PDUs)    -   Reordering function (PDCP PDU reordering for reception)    -   Duplicate detection function (Duplicate detection of lower layer        SDUs)    -   Retransmission function (Retransmission of PDCP SDUs)    -   Ciphering and deciphering function (Ciphering and deciphering)    -   Timer-based SDU discard function (Timer-based SDU discard in        uplink)

In this case, the reordering function of the NR PDCP apparatus refers toa function of reordered PDCP PDUs received in a lower layer in orderbased on a PDCP sequence number (SN) and may include a function oftransferring data to the upper layer in the reordered order, a functionof recording PDCP PDUs missed by the reordering, a function of reportinga state of the missed PDCP PDUs to a transmitting side, and a functionof requesting a retransmission of the missed PDCP PDUs.

The main functions of the NR RLCs 3 d-10 and 3 d-35 may include some ofthe following functions.

-   -   Data transfer function (Transfer of upper layer PDUs)    -   In-sequence delivery function (In-sequence delivery of upper        layer PDUs)    -   Out-of-sequence delivery function (Out-of-sequence delivery of        upper layer PDUs)    -   ARQ function (Error correction through HARQ)    -   Concatenation, segmentation, reassembly function (Concatenation,        segmentation and reassembly of RLC SDUs)    -   Re-segmentation function (Re-segmentation of RLC data PDUs)    -   Reordering function (Reordering of RLC data PDUs)    -   Duplicate detection function (Duplicate detection)    -   Error detection function (Protocol error detection)    -   RLC SDU discard function (RLC SDU discard)    -   RLC re-establishment function (RLC re-establishment)

In this case, the in-sequence delivery function of the NR RLC apparatusrefers to a function of delivering RLC SDUs received from a lower layerto an upper layer in order, and may include a function of reassemblingand transferring an original one RLC SDU which is divided into aplurality of RLC SDUs and received. The NR RLC may include a function ofreorder the received RLC PDUs based on the RLC sequence number (SN) orthe PDCP sequence number (SN) and a function of recording the RLC PDUsmissed by the reordering. The NR RLC may include a function of reportinga state of the missed RLC PDUs to the transmitting side and a functionof requesting a retransmission of the missed RLC PDUs. The NR RLC mayinclude a function of transferring only the SLC SDUs before the missedRLC SDU to the upper layer in order when there is the missed RLC SDU anda function of transferring all the received RLC SDUs to the upper layerbefore a predetermined timer starts if the timer expires even if thereis the lost RLC SDU. Alternatively, the NR RLC may include a function oftransferring all the RLC SDUs received until now to the upper layer inorder if the predetermined timer expires even if there is the missed RLCSDU. Further, the NR RLC may process the RLC PDUs in the received order(in order of arrival regardless of the order of a serial number and thesequence number), and may transmit the processed RLC PDUs to the PDCPapparatus the out-of-sequence delivery. In the case of the segment, theNR RLC may receive the segments which are stored in the buffer or is tobe received later and reconfigure the RLC PDUs into one complete RLC PDUand then transmit the complete RLC PDU to the PDCP apparatus. The NR RLClayer may not include the concatenation function and may perform thefunction in the NR MAC layer or may be replaced by the multiplexingfunction of the NR MAC layer.

In this case, the out-of-sequence delivery function of the NR RLCapparatus refers to a function of directly delivering the RLC SDUsreceived from the lower layer to the upper layer regardless of order.The NR RLC may include a function of reassembling and transferring anoriginal one RLC SDU which is divided into several RLC SDUs andreceived, and a function of storing and reordering the RLC SN or thePDCP SP of the received RLC PDUs to record the missed RLC PDUs.

The NR MACs 3 d-15 and 3 d-30 may be connected to several NR RLC layerapparatus configured in one terminal, and the main functions of the NRMAC may include some of the following functions.

-   -   Mapping function (Mapping between logical channels and transport        channels)    -   Multiplexing and demultiplexing function        (Multiplexing/demultiplexing of MAC SDUs)    -   Scheduling information reporting function (Scheduling        information reporting)    -   HARQ function (Error correction through HARQ)    -   Priority handling function between logical channels (Priority        handling between logical channels of one UE)    -   Priority handling function between terminals (Priority handling        between UEs by means of dynamic scheduling)    -   MBMS service identification function (MBMS service        identification)    -   Transport format selection function (Transport format selection)    -   Padding function (Padding)

The NR PHY layers 3 d-20 and 3 d-25 may perform an operation ofchannel-coding and modulating higher layer data, making the higher layerdata as an OFDM symbol and transmitting them to a radio channel, ordemodulating and channel-decoding the OFDM symbol received through theradio channel and transmitting the demodulated and channel-decoded OFDMsymbol to the higher layer.

FIGS. 3EA-3EB are diagrams illustrating a structure of processing datain the LTE system.

As shown in FIGS. 3EA-3EB, in the LTE system, the data processing isperformed in the PDCP layer and the RLC layer for each logical channel.That is, the logical channel 1 3 e-05 and the logical channel 3 3 e-10have different PDCP layers and RLC layers and perform independent dataprocessing. Then, the RLC PDU generated from the RLC layer of eachlogical channel is transmitted to the MAC layer, which is configured asone MAC PDU, and then transmitted to the receiving end. In the LTEsystem, the PDCP layer, the RLC layer, and the MAC layer may include thefunctions described with reference to FIG. 3B, and may performcorresponding operations.

The LTE system may be characterized in that the PDCP PDUs concatenate inthe RLC layer and in the MAC PDU structure as shown in 3 e-25, all theMAC subheaders are located at the head part and the MAC SDU part islocated at the tail part of the MAC PDU. Due to the abovecharacteristics, in the LTE system, the data processing may be performedin advance or prepared in the RLC layer before the uplink transmissionresource (uplink grant) is received. If receiving the uplinktransmission resource 3 e-30 as shown in FIG. 3E, the terminalconcatenates the PDCP PDUs received from the PDCP layer according to theuplink transmission resource to generate the RLC PDU. The uplinktransmission resources are received from the base station in the MAClayer and then subjected to logical channel prioritization (LCP), andthe uplink transmission resources are allocated to each logical channel.That is, the uplink transmission resource 3 e-30 is the uplinktransmission resource allocated from the MAC layer. If the size of thePDCP PDUs to be concatenated does not match the uplink transmissionresource, the RLC layer performs a segmentation procedure to match thePDCP PDUs with the uplink transmission resources. The above proceduremay be performed for each logical channel, and each RLC apparatus canconfigure an RLC header using the concatenated PDCP PDUs and transmitthe completed RLC PDU to the MAC apparatus. The MAC apparatus mayconfigure the RLC PDUs (MAC SDUs) received from each RLC layer as oneMAC PDU and transmit the MAC PDU to the PHY apparatus. When the RLCapparatus performs a segmentation operation when configuring the RLCheader and includes the segmented information in the header, the MACapparatus may include the length information of each of the concatenatedPDCP PDUs in the header (which is to be reassembled at the receivingend).

As described above, in the LTE system, the data processing of the RLClayer, the MAC layer, and the PHY layer starts from the time when theuplink transmission resource is received.

In the LTE system, the RLC layer may operate in an RLC acknowledged mode(AM) mode, an RLC unacknowledged mode (UM) mode, and an RLC transparentmode (TM) mode. In the RLC AM mode, the RLC layer supports the ARQfunction, the transmitting end may receive the RLC status report fromthe receiving end and perform the retransmission on the RLC PDUs thatreceive the NACK through the status report. Accordingly, reliable datatransmission may be achieved without error. Therefore, it is suitablefor a service requiring high reliability. On the other hand, the ARQfunction is not supported in the RLC UM mode. Therefore, the RLC statusreport is not received and there is no retransmission function. In theRLC UM mode, when the uplink transmission resource is received, thetransmitting end RLC layer concatenates the PDCP PDUs (RLC SDUs)received from the upper layer and transmits the received PDCP PDUs tothe lower layer. Therefore, the data can be continuously transmittedwithout the transmission delay and can be useful for a service sensitiveto the transmission delay. In the RLC TM mode, the RLC layer directlytransmits the PDCP PDUs received from the upper layer to the lower layerwithout performing any processing. That is, in the TM mode of the RLClayer, the data from the upper layer is transparently transmitted to thelower layer in the RLC layer. Therefore, it can be useful fortransmitting system information, paging message, or the like transmittedon a common channel such as a common control channel (CCCH).

FIGS. 3FA-3FB are diagrams illustrating a structure of processing datain the next generation mobile communication system of the presentdisclosure.

As shown in FIGS. 3FA-3FB, in the next generation mobile communicationsystem, the data processing is performed in the PDCP layer and the RLClayer for each logical channel. That is, the logical channel 1 3 f-05and the logical channel 3 3 f-10 have different PDCP layers and RLClayers and perform independent data processing. Then, the RLC PDUgenerated from the RLC layer of each logical channel is transmitted tothe MAC layer, which is configured as one MAC PDU, and then transmittedto the receiving end. In the LTE system, the PDCP layer, the RLC layer,and the MAC layer may include the functions described with reference toFIG. 3D, and may perform corresponding operations.

The next generation mobile communication system may be characterized inthat the PDCP PDUs concatenate in the RLC layer and in the MAC PDUstructure as shown in 3 f-25, the MAC subheaders have for each MAC SDU,that is, are repeated in units of the MAC sub-header and the MAC SDU.Therefore, in the next generation mobile communication system, as shownin 3 f-30, the data may be pre-processed in advance before receiving theuplink transmission resource. That is, if the terminal receives an IPpacket from the PDCP layer before receiving the UL grant, the terminalmay perform the PDCP processing (ciphering, integrity protection, or thelike) on the IP packet, generate a PDCP header to generate the PDCP PDU,and transmit the PDCP PDU to the RLC layer to configure the RLC header,and transmit the RLC PDU to the MAC layer to configure the MAC subheaderand the MAC SDU in advance.

If the terminal receives the uplink transmission resource 3 f-30, theterminal may configure the MAC PDU by fetching the MAC subheaders andthe MAC SDUs corresponding to the size of the uplink transmissionresource, and if the uplink transmission resource is not sufficient, thesegmentation operation may be performed to fully fill and efficientlyuse the transmission resources. Then, the corresponding RLC header(segmented information or length information) and MAC header (since theL field and length are changed) corresponding thereto can be updated (3f-40). Therefore, assuming that the NR system receives the uplinktransmission resources at the same time points 3 f-30 and 3 f-45 ascompared with the LTE system, the next generation mobile communicationsystem may have a large gain in a processing time like 3 f-35. The RLClayer and the PDCP layer may use a common serial number if necessary orwhen configured by a network.

The pre-processing operation may be performed for each logical channel,and the RLC PDUs pre-processed for each logical channel may bepre-processed to MAC SDUs and MAC subheaders in the MAC layer. Inaddition, if the MAC layer receives the uplink transmission resource 3f-30, the terminal may allocate the uplink transmission grant to eachlogical channel and multiplex the MAC SDUs and MAC sub-headers generatedin advance. After receiving the uplink transmission resource from thebase station, the terminal performs the logical channel prioritization(LCP) in the MAC layer, and allocates the uplink transmission resourcesto each logical channel. The terminal multiplexes the MAC SDUs and theMAC subheaders generated for each logical channel to form one MAC PDUand transmits the MAC PDU to the PHY layer. If the uplink transmissionresources allocated to each logical channel are insufficient, theterminal may perform the segmentation request to the RLC layer and ifthe segmentation operation is performed in the RLC layer, the terminalincludes the segmented information in the header and updates thesegmented information and transmits the segmented information to the MAClayer again, in which the MAC layer may update the MAC headercorresponding thereto. That is, the next generation mobile communicationsystem starts the data processing of the PDCP layer, the RLC layer, andthe MAC layer starts before receiving the uplink transmission resource.

In the next generation mobile communication system, the RLC layer mayoperate in an RLC acknowledged mode (AM) mode, an RLC unacknowledgedmode (UM) mode, and an RLC transparent mode (TM) mode. In the RLC AMmode, the RLC layer supports the ARQ function, the transmitting end mayreceive the RLC status report from the receiving end and perform theretransmission on the RLC PDUs that receive the NACK through the statusreport. Accordingly, reliable data transmission may be achieved withouterror. Therefore, it is suitable for a service requiring highreliability. On the other hand, the ARQ function is not supported in theRLC UM mode. Therefore, the RLC status report is not received and thereis no retransmission function. In the RLC UM mode, when the uplinktransmission resource is received, the transmitting end RLC layerconcatenates the PDCP PDUs (RLC SDUs) received from the upper layer andtransmits the received PDCP PDUs to the lower layer. Therefore, the datacan be continuously transmitted without the transmission delay and canbe useful for a service sensitive to the transmission delay. In the RLCTM mode, the RLC layer directly transmits the PDCP PDUs received fromthe upper layer to the lower layer without performing any processing.That is, in the TM mode of the RLC layer, the data from the upper layeris transparently transmitted to the lower layer in the RLC layer.Therefore, it can be useful for transmitting system information, pagingmessage, or the like transmitted on a common channel such as a commoncontrol channel (CCCH).

In the next generation mobile communication system, the RLC layeridentifies the successful transmission of the transmitted RLC PDU forthe RLC AM mode and, if there are missed RLC PDUs, a polling method isused so that the transmitting end reports the missed RLC PDUs from thereceiving end for retransmission. That is, when the polling is triggeredin the transmitting end, the RLC layer sets a poll bit having a lengthof 1 bit in the header of the RLC PDU to be 1 to request the receivingend to report the status report for the ACK/NACK of the RLC PDUsreceived so far. Upon receiving the RLC PDU in which a poll bit is setto be ‘1’, the receiving end creates an RLC status report to formACK/NACK information for the RLC PDUs received so far and transmit theACK/NACK information to the transmitting end. Upon receiving the RLCstatus report, the transmitting end performs the retransmission for theRLC PDUs determined to be NACK to prevent the missed RLC PDU fromoccurring.

The conditions under which the RLC layer triggers the polling are asfollows.

1. When the total number of transmitted RLC PDUs is greater than apredetermined number,

2. If the total amount/bytes of the transmitted RLC PDUs is greater thanthe predetermined amount/byte,

3. If the buffer is empty, that is, the last RLC PDU is transmitted,

4. If the window is stalled and cannot transmit a new RLC PDU,

5. If the poll retransmission timer (t-pollRetransmit) expires.

As described above, there are many conditions for the RLC layer totrigger polling, and data pre-processing is possible in the nextgeneration mobile communication system as described in FIGS. 3FA-3FB.That is, since the next generation mobile communication system has thestructure as illustrated in FIGS. 3FA-3FB, several RLC PDUs may enterone MAC PDU. Since there is a concatenation function in the RLC layer inthe LTE system as illustrated in FIGS. 3EA-3EB, a plurality of PDCP PDUsare concatenated to form one RLC PDU, which is in turn transmitted tothe MAC layer. Therefore, one MAC PDU usually includes RLC PDUscorresponding to the number of logical channels (in the LTE system, thenumber of logical channels is generally about 2 to 4). However, in thenext generation mobile communication system, one PDCP PDU is generatedas one RLC PDU since there is no RLC concatenation function in the RLClayer. Therefore, the RLC PDUs may be included in one MAC PDU by thenumber obtained by multiplying the IP packet (PDCP SDU) by the number oflogical channels. In a simple arithmetic calculation, at most four RLCPDUs may be included in one MAC PDU in the LTE system, while in the nextgeneration mobile communication system, more than 500 RLC PDUs may beincluded in one MAC PDU.

Therefore, due to the polling triggering conditions in the RLC layerdescribed above, a plurality of polling may be unnecessarily set in theRLC layer. However, this is not a big problem. The header of the RLC PDUheader has a poll bit, which needs to be set to 0 or 1 and transmittedanyway. Therefore, the receiving end may preferable to solve the problemdue to the setting of the plurality of poll bits as described above.

In addition, as described above, in the next generation mobilecommunication system, data pre-processing can be performed. Therefore,if the RLC layer sets the poll bit in the RLC PDU and then drives thepolled retransmission timer (t-pollRetransmit), the pollingretransmission timer may expire quickly and the polling may need to beagain transmitted unnecessarily because the RLC PDU in which the pollingis set may be greatly different in time from the actual transmissiontime.

The present disclosure proposes an RLC polling method considering datapre-processing in a next generation mobile communication system, andmore specifically, proposes a method of driving two timers, a pollingretransmission timer (t-pollingRetransmit) and an RLC status reportprevention timer (t-StatusProhibit). In addition, we propose tointroduce a polling prevention timer into the transmitting end as onemethod.

Since the data pre-processing can be performed in the next generationmobile communication system, the transmitting end RLC layer needs todrive the polling retransmission timer not at the time of transmittingthe RLC PDU in which the polling is set to the lower layer but at thetime of transmitting the RLC PDU in which the polling is set byincluding the RLC PDU in the MAC PDU actually receiving the uplinktransmission resource. If the polling retransmission timer is driven orupdated at the time of transmitting the RLC PDU including the polling tothe lower layer in the RLC layer, the next generation mobilecommunication system can perform the data pre-processing. Therefore, thepolling retransmission timer is updated several times while theplurality of RLC PDUs in which the polling is set are transmitted to thelower layer. As a result, the polling retransmission timer expires lateand the function thereof cannot be performed properly. On the otherhand, since the data pre-processing cannot be performed in the LTEsystem, the fact that the transmitting end RLC layer transmits the RLCPDU in which the polling is set means that it is configured to bedirectly included in the MAC PDU and transmitted. Therefore, it isreasonable to drive the polling retransmission timer at the time oftransmitting the RLC PDU in which the polling is set to the RLC PDU.

By driving the polling retransmission timer as described above, if theRLC status report does not come until the transmission end configuresthe polling and the predetermined time has elapsed, that is, until thepolling retransmission timer expires, the polling may be immediatelyreset and transmitted.

As described above, in the next generation mobile communication system,the RLC PDUs in which many unnecessary pollings are set may betransmitted to the receiving end.

The present disclosure proposes an embodiment for solving the problemcaused due to many unnecessary pollings in the next generation mobilecommunication system.

This embodiment proposes a method of processing many unnecessarypollings at the receiving end. Since the polling bit is set to be 1 inthe RLC header of the RLC PDU to be transmitted when the polling istransmitted from the transmitting end to the receiving end, even thoughseveral pollings are transmitted, there is no loss in terms of overhead.Therefore, a method for reasonably processing at the receiving end isproposed. The problem that can arise when the receiving end receives theplurality of pollings is that the receiving end may perform theplurality of RLC status reports. That is, when it is confirmed that thepoll bit is set to 1 in the RLC PDU, the receiver configures ACK/NACKinformation for the recently received RLC PDUs and transmits theACK/NACK information to the transmitter. If the plurality of RLC statusreports are transmitted, the unnecessary overhead occurs and theprocessing time is wasted at the receiving end. Accordingly, when theRLC status report prevention timer (t-StatusProhibit) is driven, the RLCstatus report prevention timer may be driven when the RLC status reportis configured and completed and is transmitted to the lower layer andthe RLC status report is triggered by the polling. If the RLC statusreport prevention timer is driven, the receiving end does not generatethe RLC status report any more until the RLC status report preventiontimer expires. Therefore, it is possible to prevent unnecessary RLCstatus reports from being generated and transmitted.

The present disclosure proposes an embodiment for solving the problemcaused due to many unnecessary pollings in the next generation mobilecommunication system.

This embodiment introduces and drives a polling prevention timer(t-pollProhibit) in order to prevent the plurality of pollings fromoccurring at the transmitting end. That is, when the condition fortriggering polling occurs in the RLC layer when data pre-processing isperformed, the polling bit is set to be 1 in one RLC PDU to betransmitted to the lower layer, and the polling prevention timer may bedriven at the time of transmitting the RLC PDU in which the polling isset is transmitted to the lower layer. Therefore, if the pollingprevention timer is driven, the polling is not set at the transmittingterminal even if the polling triggering condition is satisfied until thepolling prevention timer expires. The polling may be transmitted afterthe polling prevention timer expires. If necessary, the polling may beperiodically transmitted when the polling prevention timer expires. Thepurpose of the polling prevention timer is two. First, when manyunnecessary pollings are prevented from being set and the plurality ofpollings are set due to the data pre-processing, the pollingretransmission timer is continuously updated due to the plurality ofpollings and as a result is prevented from expiring too late.

In the present disclosure, for the RLC polling method considering thedata pre-processing in the next generation mobile communication systemas described above, the time and method for driving the pollingretransmission (t-pollingRetransmit), the RLC status report preventiontimer (t-StatusProhibit), and the polling prevention timer(t-pollProhibit) are proposed. Since the next generation mobilecommunication system terminal may perform multiple access to the LTEsystem and the next generation mobile communication system, differentRLC layers need to be operated differently within one terminal. That is,the RLC layers need to differently drive the timers depending on whetherthe timers are connected to the LTE system or the next generation mobilecommunication system.

FIG. 3G is a diagram illustrating a scenario in which a terminal isconnected to an LTE system (LTE eNB) and a next generation mobilecommunication system (NR gNB) by a multiple access.

As illustrated in FIG. 3G, the terminal may establish the LTE systembase station as a master base station and the next generation mobilecommunication system base station as a secondary base station to performthe multiple access (3 g-05), and the terminal may establish the nextgeneration mobile communication system base station as the master basestation and the LTE system base station as the secondary base station toperform the multiple access (3 g-10).

As described above, when the terminal is connected to the LTE systembase station and the next generation mobile communication system by themultiple access, a method for driving each timer differently in each RLClayer as follows.

If satisfying the first condition, the terminal performs the firstoperation,

If satisfying the second condition, the terminal performs the secondoperation,

If satisfying the third condition, the terminal performs the thirdoperation,

If satisfying the fourth condition, the terminal performs the fourthoperation,

In this case, the first condition means the case where the terminaltransmits data on the uplink and the connection for transmitting thedata is connected to the LTE system.

In this case, the second condition means the case where the terminaltransmits data on the uplink and the connection for transmitting thedata is connected to the next generation mobile communication system.

In this case, the third condition means the case where the terminalreceives data on the uplink and the connection for receiving the data isconnected to the LTE system.

In this case, the fourth condition means the case where the terminalreceives data on the uplink and the connection for receiving the data isconnected to the next generation mobile communication system.

According to the first operation, when the polling triggering conditionis satisfied in the RLC layer, the terminal sets the poll bit to be 1 inthe RLC header of the RLC PDU and transmits the poll bit to the lowerlayer, and drives the polling retransmission timer at the time oftransmitting the RLC PDU in which the polling is set to the lower layer.

According to the second operation, when the polling triggering conditionis satisfied in the RLC layer, the terminal sets the poll bit to be 1 inthe RLC header of the RLC PDU and transmits the poll bit to the lowerlayer, and drives the polling retransmission timer at the time oftransmitting the RLC PDU in which the polling is set to the lower layer.

According to the third operation, if the terminal receives the pollingfrom the RLC layer, the terminal configures the RLC status report anddrives the RLC status report prevention timer at the time oftransmitting the configured RLC status report to the lower layer ortriggering the RLC status report due to the polling.

According to the third operation, if the terminal receives the pollingfrom the RLC layer, the terminal configures the RLC status report anddrives the RLC status report prevention timer at the time oftransmitting the configured RLC status report to the lower layer ortriggering the RLC status report due to the polling.

As described above, when the terminal is connected to the LTE systembase station and the next generation mobile communication system by themultiple access, an embodiment for a method for driving each timerdifferently in each RLC layer as follows.

If satisfying the first condition, the terminal performs the firstoperation,

If satisfying the second condition, the terminal performs the secondoperation,

If satisfying the third condition, the terminal performs the thirdoperation,

If satisfying the fourth condition, the terminal performs the fourthoperation,

According to the first condition, the terminal transmits data to theuplink and the connection for transmitting the data refers to the casein which the terminal is connected to the LTE system.

According to the second condition, the terminal transmits data to theuplink and the connection for transmitting the data refers to the casein which the terminal is connected to the next generation mobile system.

According to the third condition, the terminal transmits data to thedownlink and the connection for receiving the data refers to the case inwhich the terminal is connected to the LTE system.

According to the fourth condition, the terminal transmits data to thedownlink and the connection for receiving the data refers to the case inwhich the terminal is connected to the next generation mobile system.

According to the first operation, when the polling triggering conditionis satisfied in the RLC layer, the terminal sets the poll bit to be 1 inthe RLC header of the RLC PDU and transmits the poll bit to the lowerlayer, and drives the polling retransmission timer at the time oftransmitting the RLC PDU in which the polling is set to the lower layer.

According to the second operation, when the polling triggering conditionis satisfied in the RLC layer, the terminal sets the poll bit to be 1 inthe RLC header of the RLC PDU and transmits the poll bit to the lowerlayer, and drives the polling retransmission timer at the time oftransmitting the RLC PDU in which the polling is set to the lower layer.The polling prevention timer is driven at the time of transmitting theRLC PDU in which the polling is set to the lower layer.

According to the third operation, if the terminal receives the pollingfrom the RLC layer, the terminal configures the RLC status report anddrives the RLC status report prevention timer at the time oftransmitting the configured RLC status report to the lower layer ortriggering the RLC status report due to the polling.

According to the third operation, if the terminal receives the pollingfrom the RLC layer, the terminal configures the RLC status report anddrives the RLC status report prevention timer at the time oftransmitting the configured RLC status report to the lower layer ortriggering the RLC status report due to the polling.

FIG. 3H is a diagram illustrating an operation of a terminal accordingto various embodiments which are a method of operating each timerdifferently in each RLC layer when the terminal is connected to the LTEsystem base station and the next generation mobile communication systemby a multiple access.

According to various embodiments described with reference to FIG. 3H,the terminal performs the first operation if the first condition issatisfied, the second operation if the second condition is satisfied,the third operation if the third condition is satisfied, and performsthe fourth operation if the fourth condition is satisfied.

FIG. 3I is a diagram illustrating a procedure for establishing aconnection between a base station and a terminal in the presentdisclosure.

In FIG. 3I, the base station can transmit an RRCConnectionReleasemessage to the terminal if the terminal transmitting and receiving datain the RRC connection mode does not transmit or receive data for apredetermined reason or for a predetermined time to switch the terminalto RRC idle mode (3 i-01). If the terminal (hereinafter, idle mode UE)that is not currently connected generates data to be transmitted later,the terminal performs an RRC connection setup procedure with the basestation. The terminal establishes uplink transmission synchronizationwith the base station through a random access procedure and transmits anRRCConnectionRequest message to the base station (3 i-05). The messageincludes establishmentCause of connection with the identifier of theterminal. The base station transmits an RRCConnectionSetup message toallow the terminal to set the RRC connection (3 i-10). The messageincludes the setting for the timers to be used in the RLC device, thevalue for the timers, that is, the polling retransmission timer(t-pollRetransmit), the polling prevention timer (t-pollProhibit), theRLC status report timer (t-StatusProhibit) or the like and may set thevalued therefor. The RRC connection is also called a signaling radiobearer (SRB) and is used for transmission and reception of the RRCmessage that is a control message between the terminal and the basestation. The terminal establishing the RRC connection transmits anRRCConnetionSetupComplete message to the base station (3 i-15). Themessage includes a control message called a service request that thatallows the terminal to request a bearer setup for a predeterminedservice to the MME. The base station transmits a service request messageincluded in the RRCConnectionSetupComplete message to the MME (3 i-20)and the MME determines whether to provide the service the terminalrequests As the determination result, if the MME decides to provide theservice that the terminal requests, the MME transmits an initial contextsetup request message to the base station (3 i-25). The initial contextsetup request message may include information such as quality of service(QoS) information to be applied when setting up a data radio bearer(DRB) and security related information (e.g., security key, securityalgorithm) to be applied to the DRB. The base station exchanges aSecurityModeCommand) message 3 i-30 and a SecurityModeComplete message 3i-35 with the terminal to establish security. When the securityestablishment is completed, the base station transmits anRRCConnectionReconfiguration message to the terminal (3 i-40). Themessage may include the setting for the timers to be used in the RLCdevice, the value for the timers, that is, the polling retransmissiontimer (t-pollRetransmit), the polling prevention timer (t-pollProhibit),the RLC status report timer (t-StatusProhibit) or the like and may setthe valued therefor (3 i-45). The base station that completes the DRBsetup with the terminal transmits an initial context response message tothe MME (3 i-50) and the MME receiving the message exchanges an S1bearer setup message and an S1 bearer setup response message with theS-GW to setup an S1 bearer (3 i-55 and 3 i-60). The S1 bearer is a datatransmission connection established between the S-GW and the basestation and corresponds to a DRB on a one-to-one basis. If all of theprocedures are completed, the terminal transmits and receives data toand from the BS through the S-GW (3 i-65 and 3 i-70). As describedabove, the normal data transmission procedure largely consists of threestages: RRC connection setup, security setup, and DRB setup. Inaddition, the base station may transmit an RRCConnectionReconfigurationmessage to renew, add, or change the configuration to the terminal for apredetermined reason (3 i-75). The message includes the setting for thetimers to be used in the RLC device, the value for the timers, that is,the polling retransmission timer (t-pollRetransmit), the pollingprevention timer (t-pollProhibit), the RLC status report timer(t-StatusProhibit) or the like and may set the valued therefor.

FIG. 3J is a diagram illustrating the structure of the terminal to whichthe embodiment of the present disclosure may be applied.

Referring to FIG. 7J, the terminal includes a radio frequency (RF)processor 3 j-10, a baseband processor 3 j-20, a memory 3 j-30, and acontroller 3 j-40.

The RF processor 3 j-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 3 j-10 up-converts a baseband signal providedfrom the baseband processor 3 j-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. Forexample, the RF processor 3 j-10 may include a transmitting filter, areceiving filter, an amplifier, a mixer, an oscillator, a digital toanalog converter (DAC), an analog to digital converter (ADC), or thelike. In the above figure, only one antenna is illustrated, but theterminal may include a plurality of antennas. Further, the RF processor3 j-10 may include a plurality of RF chains. Further, the RF processor 3j-10 may perform beamforming. For the beamforming, the RF processor 3j-10 may adjust a phase and a size of each of the signals transmittedand received through a plurality of antennas or antenna elements. Inaddition, the RF processor may perform MIMO and may receive a pluralityof layers when performing a MIMO operation. The RF processor 3 j-10 mayperform reception beam sweeping by appropriately configuring a pluralityof antennas or antenna elements under the control of the controller oradjust a direction and a beam width of the reception beam so that thereception beam is resonated with the transmission beam.

The baseband processor 3 j-20 performs a conversion function between abaseband signal and a bit string according to a physical layer standardof a system. For example, when data are transmitted, the basebandprocessor 3 j-20 generates complex symbols by coding and modulating atransmitted bit string. Further, when data are received, the basebandprocessor 3 j-20 recovers the received bit string by demodulating anddecoding the baseband signal provided from the RF processor 3 j-10. Forexample, according to the orthogonal frequency division multiplexing(OFDM) scheme, when data are transmitted, the baseband processor 3 j-20generates the complex symbols by coding and modulating the transmittingbit string, maps the complex symbols to sub-carriers, and then performsan inverse fast Fourier transform (IFFT) operation and a cyclic prefix(CP) insertion to configure the OFDM symbols. Further, when data arereceived, the baseband processor 3 j-20 divides the baseband signalprovided from the RF processor 3 j-10 in an OFDM symbol unit andrecovers the signals mapped to the sub-carriers by a fast Fouriertransform (FFT) operation and then recovers the received bit string bythe modulation and decoding.

The baseband processor 3 j-20 and the RF processor 3 j-10 transmit andreceive a signal as described above. Therefore, the baseband processor 3j-20 and the RF processor 3 j-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. Further, at least oneof the baseband processor 3 j-20 and the RF processor 3 j-10 may includea plurality of communication modules to support a plurality of differentradio access technologies. Further, at least one of the basebandprocessor 3 j-20 and the RF processor 3 j-10 may include differentcommunication modules to process signals in different frequency bands.For example, the different wireless access technologies may include anLTE network, an NR network, and the like. Further, different frequencybands may include a super high frequency (SHF) (for example: 2.5 GHz, 5GHz) band, a millimeter wave (for example: 60 GHz) band.

The memory 3 j-30 stores data such as basic programs, applicationprograms, and configuration information for the operation of theterminal. Further, the memory 3 j-30 provides the stored data accordingto the request of the controller 3 j-40.

The controller 3 j-40 controls the overall operations of the terminal.For example, the controller 3 j-40 transmits and receives a signalthrough the baseband processor 3 j-20 and the RF processor 3 j-10.Further, the controller 3 j-40 records and reads data in and from thememory 3 j-30. For this purpose, the controller 3 j-40 may include atleast one processor. For example, the controller 3 j-40 may include acommunication processor (CP) performing a control for communication andan application processor (AP) controlling a higher layer such as theapplication programs. According to the embodiment of the presentdisclosure, the controller 3 j-40 includes a multi-link processor 3 j-42that performs the processing to be operated in a multi-link mode.

FIG. 3K illustrates a block configuration diagram of the TRP in thewireless communication system to which the embodiment of the presentdisclosure may be applied.

As illustrated in FIG. 3K, the base station is configured to include anRF processor 3 k-10, a baseband processor 3 k-20, a communication unit 3k-30, a memory 3 k-40, and a controller 3 k-50.

The RF processor 3 k-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 3 k-10 up-converts a baseband signal providedfrom the baseband processor 3 k-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. Forexample, the RF processor 3 k-10 may include a transmitting filter, areceiving filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,or the like. In the above figure, only one antenna is illustrated, butthe first access node may include a plurality of antennas. Further, theRF processor 3 k-10 may include a plurality of RF chains. Further, theRF processor 3 k-10 may perform the beamforming. For the beamforming,the RF processor 3 k-10 may adjust a phase and a size of each of thesignals transmitted/received through a plurality of antennas or antennaelements. The RF processor may perform a downward MIMO operation bytransmitting one or more layers.

The baseband processor 3 k-20 performs a conversion function between thebaseband signal and the bit string according to the physical layerstandard of the first radio access technology. For example, when dataare transmitted, the baseband processor 3 k-20 generates complex symbolsby coding and modulating a transmitted bit string. Further, when dataare received, the baseband processor 3 k-20 recovers the received bitstring by demodulating and decoding the baseband signal provided fromthe RF processor 3 k-10. For example, according to the OFDM scheme, whendata are transmitted, the baseband processor 3 k-20 generates thecomplex symbols by coding and modulating the transmitting bit string,maps the complex symbols to the sub-carriers, and then performs the IFFToperation and the CP insertion to configure the OFDM symbols. Further,when data are received, the baseband processor 3 k-20 divides thebaseband signal provided from the RF processor 3 k-10 in the OFDM symbolunit and recovers the signals mapped to the sub-carriers by the FFToperation and then recovers the receiving bit string by the modulationand decoding. The baseband processor 3 k-20 and the RF processor 3 k-10transmit and receive a signal as described above. Therefore, thebaseband processor 3 k-20 and the RF processor 3 k-10 may be called atransmitter, a receiver, a transceiver, or a communication unit.

The communication unit 3 k-30 provides an interface for performingcommunication with other nodes within the network.

The memory 3 k-40 stores data such as basic programs, applicationprograms, and configuration information for the operation of the mainbase station. In particular, the memory 3 k-40 may store the informationon the bearer allocated to the accessed terminal, the measured resultsreported from the accessed terminal, etc. Further, the memory 3 k-40 maystore information that is a determination criterion on whether toprovide a multiple connection to the terminal or stop the multipleconnection to the terminal. Further, the memory 3 k-40 provides thestored data according to the request of the controller 3 k-50.

The controller 3 k-50 controls the general operations of the main basestation. For example, the controller 3 k-50 transmits/receives a signalthrough the baseband processor 3 k-20 and the RF processor 3 k-10 or thebackhaul communication unit 3 k-30. Further, the controller 3 k-50records and reads data in and from the memory 3 k-40. For this purpose,the controller 3 k-50 may include at least one processor. According tothe embodiment of the present disclosure, the controller 3 k-50 includesa multi-link processor 3 k-52 that performs the processing to beoperated in a multi-link mode.

FIG. 4A is a diagram illustrating a structure of an LTE systemreferenced for the explanation of the present disclosure.

As illustrated in FIG. 4A, a radio access network of an LTE system isconfigured to include next generation base stations (evolved node B,hereinafter, eNB, Node B, or base station) 4 a-05, 4 a-10, 4 a-15, and 4a-20, a mobility management entity (MME) 4 a-25, and a serving-gateway(S-GW) 4 a-30. User equipment (hereinafter, UE or terminal) 4 a-35accesses an external network through the eNBs 4 a-05 to 4 a-20 and theS-GW 4 a-30.

In FIG. 4A, the eNB 4 a-05 to 4 a-20 correspond to the existing node Bof the UMTS system. The eNB is connected to the UE 4 a-35 through aradio channel and performs more complicated role than the existing nodeB. In the LTE system, in addition to a real-time service like a voiceover Internet protocol (VoIP) through the Internet protocol, all theuser traffics are served through a shared channel and therefore anapparatus for collecting and scheduling status information such as abuffer status, an available transmission power status, and a channelstatus of the terminals is used. Here, the eNBs 4 a-05 to 4 a-20 takecharge of the collecting and scheduling. One eNB generally controls aplurality of cells. For example, to implement a transmission rate of 100Mbps, the LTE system uses, as a radio access technology, orthogonalfrequency division multiplexing (hereinafter, OFDM) in, for example, abandwidth of 20 MHz. Further, an adaptive modulation & coding(hereinafter, referred to as AMC) determining a modulation scheme and achannel coding rate according to a channel status of the terminal isapplied. The S-GW 4 a-30 is an apparatus for providing a data bearer andgenerates or removes the data bearer according to the control of the MME4 a-25. The MME is an apparatus for performing a mobility managementfunction for the terminal and various control functions and is connectedto a plurality of base stations.

FIG. 4B is a diagram illustrating the radio protocol structure in theLTE system referenced for the explanation of the present disclosure.

Referring to FIG. 4B, the radio protocol of the LTE system is configuredto include packet data convergence protocols (PDCPs) 4 b-05 and 4 b-40,radio link controls (RLCs) 4 b-10 and 4 b-35, and medium access controls(MACs) 4 b-15 and 4 b-30 in the terminal and the eNB, respectively. ThePDCPs 4 b-05 and 4 b-40 are in charge of operations such as IP headercompression/decompression. The main functions of the PDCP are summarizedas follows.

-   -   Header compression and decompression function (Header        compression and decompression: ROHC only)    -   Transfer function of user data (Transfer of user data)    -   In-sequence delivery function (In-sequence delivery of upper        layer PDUs at PDCP re-establishment procedure for RLC AM)    -   Reordering function (For split bearers in DC (only support for        RLC AM): PDCP PDU routing for transmission and PDCP PDU        reordering for reception)    -   Duplicate detection function (Duplicate detection of lower layer        SDUs at PDCP re-establishment procedure for RLC AM)    -   Retransmission function (Retransmission of PDCP SDUs at handover        and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery        procedure, for RLC AM)    -   Ciphering and deciphering function (Ciphering and deciphering)    -   Timer-based SDU discard function (Timer-based SDU discard in        uplink)

The radio link controls (hereinafter, referred to as RLCs) 1 b-10 and 1b-35 reconfigures the PDCP packet data unit (PDU) to an appropriate sizeto perform the ARQ operation or the like. The main functions of the RLCare summarized as follows.

-   -   Data transfer function (Transfer of upper layer PDUs)    -   ARQ function (Error Correction through ARQ (only for AM data        transfer))    -   Concatenation, segmentation, reassembly functions        (Concatenation, segmentation and reassembly of RLC SDUs (only        for UM and AM data transfer))    -   Re-segmentation function (Re-segmentation of RLC data PDUs (only        for AM data transfer))    -   Reordering function (Reordering of RLC data PDUs (only for UM        and AM data transfer)    -   Duplicate detection function (Duplicate detection (only for UM        and AM data transfer))    -   Error detection function (Protocol error detection (only for AM        data transfer))    -   RLC SDU discard function (RLC SDU discard (only for UM and AM        data transfer))    -   RLC re-establishment function (RLC re-establishment)

The MACs 4 b-15 and 4 b-30 are connected to several RLC layer devicesconfigured in one terminal and perform an operation of multiplexing RLCPDUs into a MAC PDU and demultiplexing the RLC PDUs from the MAC PDU.The main functions of the MAC are summarized as follows.

-   -   Mapping function (Mapping between logical channels and transport        channels)    -   Multiplexing/demultiplexing function        (Multiplexing/demultiplexing of MAC SDUs belonging to one or        different logical channels into/from transport blocks (TB)        delivered to/from the physical layer on transport channels)    -   Scheduling information reporting function (Scheduling        information reporting)    -   HARQ function (Error correction through HARQ)    -   Priority handling function between logical channels (Priority        handling between logical channels of one UE)    -   Priority handling function between terminals (Priority handling        between UEs by means of dynamic scheduling)    -   MBMS service identification function (MBMS service        identification)    -   Transport format selection function (Transport format selection)    -   Padding function (Padding)

Physical layers 4 b-20 and 4 b-25 perform an operation of channel-codingand modulating higher layer data, making the higher layer data as anOFDM symbol and transmitting them to a radio channel, or demodulatingand channel-decoding the OFDM symbol received through the radio channeland transmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

FIG. 4C is a diagram illustrating a structure of a next generationmobile communication system to which the present disclosure is applied.

Referring to FIG. 4C, a radio access network of a next generation mobilecommunication system is configured to include a next generation basestation (New radio node B, hereinafter NR NB or NR base station) 4 c-10and a new radio core network (NR CN) 4 c-05. The user terminal (newradio user equipment, hereinafter, NR UE or UE) 4 c-15 accesses theexternal network through the NR NB 4 c-10 and the NR CN 4 c-05.

In FIG. 4C, the NR NB 4 c-10 corresponds to an evolved node B (eNB) ofthe existing LTE system. The NR NB is connected to the NR UE 4 c-15 viaa radio channel and may provide a service superior to the existing nodeB. In the next generation mobile communication system, since all usertraffics are served through a shared channel, an apparatus forcollecting state information such as a buffer status, an availabletransmission power state, and a channel status of the UEs to performscheduling is used. The NR NB 4 c-10 may serve as the device. One NR NBgenerally controls a plurality of cells. In order to realize thehigh-speed data transmission compared with the existing LTE, the NR gNBmay have the existing maximum bandwidth or more, and may be additionallyincorporated into a beam-forming technology by using orthogonalfrequency division multiplexing (hereinafter, referred to as OFDM) as aradio access technology. Further, an adaptive modulation & coding(hereinafter, referred to as AMC) determining a modulation scheme and achannel coding rate according to a channel status of the terminal isapplied. The NR CN 4 c-05 may perform functions such as mobilitysupport, bearer setup, QoS setup, and the like. The NR CN is a devicefor performing a mobility management function for the terminal andvarious control functions and is connected to a plurality of basestations. In addition, the next generation mobile communication systemcan interwork with the existing LTE system, and the NR CN is connectedto the MME 4 c-25 through the network interface. The MME is connected tothe eNB 4 c-30 which is the existing base station.

FIG. 4D is a diagram illustrating a structure of another next generationmobile communication system to which the present disclosure may beapplied.

Referring to FIG. 4D, the cell in which the NR gNB 4 d-05 operated basedon the beam serves may be configured of a plurality of transmissionreception points 4 d-10, 4 d-15, 4 d-20, 4 d-25, 4 d-30, 4 d-35, and 4d-40. The TRPs 4 d-10 to 4 d-40 represent blocks which separate somefunctions of transmitting/receiving physical signals from the existingLTE base station (eNB) and is configured of a plurality of antennas. TheNR gNB 4 d-05 may be expressed as a central unit (CB), and the TRP maybe expressed as a distributed unit (DB). The functions of the NR gNB (4d-05) and the TRP may be configured by separating each layer in thePDCP/RLC/MAC/PHY layers like 4 d-45. That is, the TRP can perform thefunction of the corresponding layer only with the PHY layer (4 d-15, 4d-25), the TRP can perform the functions of the corresponding layersonly with the PHY layer and MAC layer 4 d-10, 4 d-35, and 4 d-40, andthe TRP may perform the functions of the corresponding layers with onlythe PHY layer, the MAC layer, and the RLC layer (4 d-20 and 4 d-30). Inparticular, the TRPs 4 d-10 and 4 d-40 may use a beamforming technologyof transmitting/receiving data by using a plurality oftransmitting/receiving antennas to generate narrow beams in severaldirections. The user terminal 4 d-50 accesses the NR gNB 4 d-05 and theexternal network through the TRPs 4 d-10 to 4 d-40. That is, in order toprovides services to users, the NR gNB 4 d-05 collects and schedulesstate information such as a buffer status, an available transmissionpower state, and a channel status of the terminals to support aconnection between the terminals and a core network (CN).

FIG. 4E is a diagram illustrating a structure of a synchronization block(SS-block) which is a subframe in which a synchronization signal istransmitted in the next generation mobile communication system.

The NR system aims at a higher transmission rate than LTE and considersscenarios operating at high frequencies to achieve wide frequencybandwidth. In particular, it is possible to consider a scenario in whicha directional beam is generated at a high frequency and data having ahigh data rate are transmitted. Accordingly, it is possible to considerscenarios in which communications are made using different beams whenthe base station or a transmission reception point (TRP) 4 e-10communicates with terminals 4 e-05 in a cell.

In the illustrated figures, the TRP 4 e-10 transmits a directionaldownlink signal through 12 beams 4 e-11 to 4 e-22. In order to measurewhich beam the terminal 4 e-05 uses to communicate with the TRP, theterminal receives a PSS 4 e-35 for timing acquisition of the symbol, anSSS 4 e-40 for detecting a cell ID, a timing of the subframe, a BRS foridentifying a beam or the like. A beam index value for identifying eachbeam from the reference signal may also be derived. In the presentillustrated figures, it is assumed that different beams are swept overevery symbol in the subframe and transmitted. The terminal 4 e-05receives a plurality of first downlink signals xSS in the first subframe4 e-30. The first subframe refers to a subframe through which aplurality of synchronization signals are transmitted, and is referred toas a synchronization signal block (SS-Block) 4 e-30. That is, theSS-Block is defined as the subframe in which the synchronization signalis transmitted among all the subframes. The first downlink signal isbased on the PSS/SSS and an ESS may be added in a high frequency using abeam, and a signal may be transmitted in a time window in which thecorresponding beam is transmitted on a beam-by-beam basis. That is, onefirst sub-frame 4 e-30 consists of n consecutive time windows (symbols),and the first downlink signal is transmitted in each time period.Alternatively, in the case of sub-6 GHz, the first downlink signal istransmitted in a first time window and other downlink signals aretransmitted in the remaining time windows. In particular, the terminal 4e-05 may receive only the first downlink signal of the servingcell/serving beam and receive the first downlink signal transmitted in abeam group consisting of a serving cell/serving beam and neighboringbeams adjacent to the serving beam. The beam group may be configured inthe base station as N best beams with good channel between the basestation and the terminal.

In the case of the channel measurement using the synchronization signalas described above, it can be particularly used for radio resourcemonitoring (RRM) measurement. That is, the channel measurement using thesynchronization signal can be used for the channel measurement of theserving cell and neighboring cells. To this end, when the channelmeasurement of the serving cell is indicated, it is useful to inform theterminal of the position of the SS-Block of the neighboring cellsnecessary for the measurement. In the present disclosure, a method forthis purpose will be described with reference to various embodiments.

FIG. 4F is a diagram illustrating an overall operation of a channelmeasurement using the synchronization signal proposed in the presentdisclosure.

A terminal 4 f-01 in an idle mode RRC_IDLE finds a suitable cell andcamps on the corresponding base station 4 f-03 (4 f-05), and receivesthe system information from the base station 4 f-10. In the idle mode,the terminal is in a state in which the terminal may not transmit databecause of not being connected to the network for power saving or thelike and is shifted to a connected mode (RRC_CONNECTED) to transmit data(4 f-15). In addition, the camping means that the terminal is staying inthe corresponding cell and receives a paging message to determinewhether data is coming on the downlink.

Then, the base station 4 f-03 transmits measurementconfiguration-related configuration information to theRRCConnectionReconfiguration message to instruct the terminal 4 f-01 tomeasure the neighboring cells. The message includes information on themeasurement object of the neighboring cells, and is transmitted by beingincluded in measObject (4 f-20). In addition, the information elementmay include an absolute radio frequency channel number (ARFCN),bandwidth information to be measured, NR-SS window information in theNR, multi-beam information, NR-SS window request information, or thelike.

In the existing LTE, the base station may set the terminal to report themeasurement information periodically or at the time of occurrence of theevent depending on the measured values of the serving cell and theneighboring cells. The event includes a case in which the followingconditions are satisfied.

-   -   Event A1: Serving becomes better than absolute threshold;    -   Event A2: Serving becomes worse than absolute threshold;    -   Event A3: Neighbor becomes amount of offset better than        PCell/PSCell;    -   Event A4: Neighbor becomes better than absolute threshold;    -   Event A5: PCell/PSCell become worse than absolute threshold1 AND        Neighbor becomes better than another absolute threshold2.    -   Event A6: Neighbor becomes amount of offset better than SCell.

In step 4 f-25, the terminal performs synchronization signal measurementon the measurement object received from the base station. The NR-SSwindow information and the NR-SS window request may be included for eachmeasurement object. The present disclosure includes a function ofreporting, by the base station, the above two measurement values as wellas a result obtained by measuring a synchronization signal measurementresult of the terminal through an automatic neighboring (ANR) function.This is activated when the base station transmits the NR-SS windowrequest in the measObject when requesting the terminal to measure theneighboring cells. The most important reason for requesting the terminalto report the NR-SS window measurement value through the ANR is that thebase station may not know the location of the SS-block of theneighboring cells. When the base station certainly knows the receptiontiming (specified by the SFN/subframe/symbol number of the PCell) of thesynchronization signal block (SS-Block) of the neighboring cells to bemeasured, the base station may transmit the corresponding information tothe terminal to instruct the neighboring cell measurement However, whenthe reception timing (specified by the SFN/subframe/symbol number ofPCell) of the synchronization signal block (SS-Block) of the neighboringcells is unknown, the corresponding information may not be transmittedto the terminal. That is, when the terminal fails to receive the NR-SSwindow information from the base station, the terminal needs to searchfor the synchronization signal over the whole area. Since theperformance of the above operation by all the terminals included in thebase station is not efficient, if the result of the search for theperformed synchronization signal is transmitted to the base station, thereception timing (specified by SFN/subframe/symbol number of PCell) ofthe synchronization signal block (SS-Block) of the meaningfulneighboring cells may be transmitted to the terminals. In addition, whenthe multi-beam information is included in the measurement value settingsignal, the terminal performs the downlink beam sweep operation inaccordance with the set multi-beam information. That is, it is possibleto perform reception beam sweeping, which is matched to receive accuratetiming and a good signal sensitivity of the signal transmitted in theset multi-beam.

In step 4 f-30, when the NR-SS window request is indicated, the terminalstores information specifying the reception time of the SS-block, inwhich the channel conditions for each cell are best, by theSFN/subframe/symbol number of the PCell and transmits the information tothe base station by including the information in the measurement valuereport in step 4 f-35. The RRC message includes the NR-SS information.Specifically, the RRC message includes information on physical cellidentity (PCI), timing information, SS-block index, and reference signalreceived power/reference signal received quality (RSRP/RSRQ) of thesynchronization signal. If the NR-SS window request information is notincluded in the measurement value setting, the terminal follows the sameprocess as the measurement value report in LTE. That is, the measurementis performed based on the periodic or event-based measurement report setby the base station, and the measurement value is reported when thecorresponding measurement report condition is satisfied. The measurementvalue report includes the physical cell identity (PCI), the measurementvalue index (measId), the cell global identity (CGI) information, andthe RSRP/RSRQ information of the synchronization signal.

FIGS. 4GA-4GB are diagrams illustrating a channel measurement andreporting operation using the synchronization signal of the terminal towhich the present disclosure is applied.

The terminal of the present disclosure learns a method for instructingand performing measurement for radio resource management (RRM) ofneighboring cells from an NR base station. In particular, themeasurement for the radio resource management is different from that inthe LTE in that the measurement is performed through the synchronizationsignal. For reference, a cell-specific reference signal (CRS) was usedto measure the neighbor cells in the LTE.

The terminal in the RRC connection state can receive the RRM measurementrequest of the neighboring cells from the base station for eachmeasurement object (4 g-05). That is, the RRCConnectionReconfigurationmessage including a measurement set value for how to measure theneighboring cells by the measObject from the base station is transmittedto the terminal. The neighboring cell measurement setup informationsignal may include an absolute radio frequency channel number (ARFCN),bandwidth information to be measured, NR-SS window information in theNR, multi-beam information, NR-SS window request information, or thelike. As described above, the information is set for each measurementobject and for each measObject. The terminal identifies whether theNR-SS window information is included the RRM measurement setup signalfor each measurement object (4 g-10). When NR-SS window information isincluded, accurately, when information (information specified bySFN/subframe/symbol number of PCell) on at which reception time thesynchronization signal in the neighboring cells to be measured may bereceived is included, the terminal measures the synchronization signalof the neighboring cells received at the corresponding set time andperforms the first operation (4 g-15). In addition, if multi-beaminformation is included in the step, the terminal performs a beam sweepoperation on the downlink reception beam. That is, it is possible toperform reception beam sweeping, which is matched to receive accuratetiming and a good signal sensitivity of the signal transmitted in theset multi-beam. When the NR-SS window request information is included inthe RRM measurement request message (4 g-20), the terminal searches forand measures the NR-SS within the set NR-SS window and stores themeasured result in the buffer together with the index of the SS-block (4g-25). In step 4 g-30, the terminal stores information for specifyingthe reception time of the SS-block having the best channel condition foreach cell by the SFN/subframe/symbol number of the PCell. In the step,the stored synchronization signal measurement value is reported to thebase station. That is, when an NR-SS request is instructed from the basestation, the terminal transmits the measured NR-SS information to thebase station. The NR-SS related measurement value report includes thephysical cell identity (PCI), the timing information, the SS-blockindex, and the RSRP/RSRQ information of the synchronization signal inneighboring cells to be measured (4 g-35). For reference, when the basestation requests the NR-SS window request, if the base station does nothave the accurate synchronous signal window (NR-SS window) informationfor the neighboring cells or is to obtain more accurate information. Ifthe base station does not include the NR-SS window request information,the terminal reports the measured value of the neighboring cellsaccording to another report condition received from the base station (4g-40). The report conditions may be set to be reported periodically orat the time of occurrence of an event according to the measurementvalues of the serving cell and the neighboring cells similarly to theLTE. The event includes a case in which the following conditions aresatisfied

-   -   Event A1: Serving becomes better than absolute threshold;    -   Event A2: Serving becomes worse than absolute threshold;    -   Event A3: Neighbor becomes amount of offset better than        PCell/PSCell;    -   Event A4: Neighbor becomes better than absolute threshold;    -   Event A5: PCell/PSCell become worse than absolute threshold1 AND        Neighbor becomes better than another absolute threshold2.    -   Event A6: Neighbor becomes amount of offset better than SCell.

That is, when the terminal satisfies the measurement report conditionset by the base station, it reports the NR-SS measurement values (RSRP,RSRQ) (4 g-40). In addition, the measurement value report includes thephysical cell identity (PCI), the measurement value index (measId), thecell global identity (CGI) information, and the RSRP/RSRQ information ofthe synchronization signal.

In addition, returning back to the step 4 g-10, when NR-SS windowinformation is not included, accurately, when information (informationspecified by SFN/subframe/symbol number of PCell) on at which receptiontime the synchronization signal in the neighboring cells to be measuredmay be received is not included, the terminal measures thesynchronization signal of the neighboring cells by performing the fullscan at all the reception time and performs the second operation (4g-45). In addition, if multi-beam information is included in the step,the terminal performs a beam sweep operation on the downlink receptionbeam. That is, it is possible to perform reception beam sweeping, whichis matched to receive accurate timing and a good signal sensitivity ofthe signal transmitted in the set multi-beam. Thereafter, when the NR-SSwindow request information is included in the RRM measurement requestmessage (4 g-50), the terminal searches for and measures the NR-SS byperforming the full scan at all the reception time and stores themeasured result in the buffer together with the index of the SS-block (4g-55). In step 4 g-60, the terminal stores information for specifyingthe reception time of the SS-block having the best channel condition foreach cell by the SFN/subframe/symbol number of the PCell. In the step,the stored synchronization signal measurement value is reported to thebase station. That is, when an NR-SS request is instructed from the basestation, the terminal transmits the measured NR-SS information to thebase station. The NR-SS related measurement value report includes thephysical cell identity (PCI), the timing information, the SS-blockindex, and the RSRP/RSRQ information of the synchronization signal inneighboring cells to be measured (4 g-65). For reference, when the basestation requests the NR-SS window request, if the base station does nothave the accurate synchronous signal window (NR-SS window) informationfor the neighboring cells or is to obtain more accurate information. Ifthe base station does not include the NR-SS window request information,the terminal reports the measured value of the neighboring cellsaccording to another report condition received from the base station.The report conditions may be set to be reported periodically or at thetime of occurrence of an event according to the measurement values ofthe serving cell and the neighboring cells similarly to the LTE. Theevent includes a case in which the following conditions are satisfied.

-   -   Event A1: Serving becomes better than absolute threshold;    -   Event A2: Serving becomes worse than absolute threshold;    -   Event A3: Neighbor becomes amount of offset better than        PCell/PSCell;    -   Event A4: Neighbor becomes better than absolute threshold;    -   Event A5: PCell/PSCell become worse than absolute threshold1 AND        Neighbor becomes better than another absolute threshold2.    -   Event A6: Neighbor becomes amount of offset better than SCell.

That is, when the terminal satisfies the measurement report conditionset by the base station, it reports the NR-SS measurement values (RSRP,RSRQ) (4 g-70). In addition, the measurement value report includes thephysical cell identity (PCI), the measurement value index (measId), thecell global identity (CGI) information, and the RSRP/RSRQ information ofthe synchronization signal.

FIGS. 4HA-4HB are diagrams illustrating a channel measurement settingand applying operation using the synchronization signal of the basestation to which the present disclosure is applied. The NR base stationin the present disclosure checks the serving cell quality state of theterminal and determines whether to measure neighboring cells (4 h-05).In this figure, the base station is instructed to perform measurementfor radio resource management (RRM) of the neighboring cells and a basestation operation using a report message received from the terminal willbe described. In particular, the measurement for the radio resourcemanagement is different from that in LTE in that the measurement isperformed through the synchronization signal. For reference, acell-specific reference signal (CRS) was used to measure the neighborcells in the LTE.

If it is determined that it is necessary to instruct the terminal tomeasure the neighboring cells in the step, the base station determineswhether the corresponding neighboring cells has the NR-SS windowinformation in step 4 h-10. If the terminal has the synchronizationsignal window information for the neighboring cells to be measured, theterminal transmits the synchronization signal window information to theterminal, including the synchronization signal window informationrelated to the measurement of the synchronization signal for thecorresponding measurement object. The neighboring cell measurement setupinformation signal may include an absolute radio frequency channelnumber (ARFCN), bandwidth information to be measured, NR-SS windowinformation in the NR, multi-beam information, NR-SS window requestinformation, or the like. In addition, it is also possible to transmitthe measurement report configuration message for allowing the terminalto report the measured value separately. The report configuration may beset to be reported periodically or at the time of occurrence of an eventaccording to the measurement values of the serving cell and theneighboring cells similarly to the LTE. In step 4 h-20, the base stationmay request the terminal to measure and report the NR-SS windowreception time according to whether the synchronization signal windowinformation of the neighboring cells is accurate or not. If the basestation requests the NR-SS window, it receives and stores the NR-SSwindow information measured and reported from the terminal for theneighboring cells that request the measurement (4 h-25). In step 4 h-30,the base station may transmit the NR-SS window information wheninstructing another terminal to perform the neighboring cell measurementusing the synchronization signal reception time information of theneighboring cells received in the step. This means that it can be usedin the neighboring cell measurement instruction step for otherterminals, that is, in steps 4 h-10. If the base station does notinclude the NR-SS window request information, the base station receivesthe measured value of the neighboring cells according to the reportconditions set from the base station. The report conditions may be setto be reported periodically or at the time of occurrence of an eventaccording to the measurement values of the serving cell and theneighboring cells similarly to the LTE (4 h-35).

If the base station does not have the synchronization signal windowinformation for the neighboring cells to be measured by the terminal instep 4 h-10, the base station transmits the synchronization signalwindow information to the terminal except for the synchronization signalwindow information (4 h-40). If the synchronization signal windowinformation is excluded, the terminal can perform a full scan for allreception times and may be defined to search for and measure asynchronization signal. The neighboring cell measurement setupinformation signal may include an absolute radio frequency channelnumber (ARFCN), bandwidth information to be measured, multi-beaminformation, NR-SS window request information, or the like. In addition,it is also possible to transmit the measurement report configurationmessage for allowing the terminal to report the measured valueseparately. The report configuration may be set to be reportedperiodically or at the time of occurrence of an event according to themeasurement values of the serving cell and the neighboring cellssimilarly to the LTE. In step 4 h-45, the base station may request theterminal to measure and report the reception time of the NR-SS window.Since the base station does not know the synchronization signalreceiving time of the neighboring cells, it is to obtain the informationthrough the terminal. If the base station requests the NR-SS window, itreceives and stores the NR-SS window information measured and reportedfrom the terminal for the neighboring cells that request the measurement(4 h-50). In step 4 h-55, the base station may transmit the NR-SS windowinformation when instructing another terminal to perform the neighboringcell measurement using the synchronization signal reception timeinformation of the neighboring cells received in the step. This meansthat it can be used in the neighboring cell measurement instruction stepfor other terminals, that is, in steps 4 h-10. If the base station doesnot include the NR-SS window request information, the base stationreceives the measured value of the neighboring cells according to thereport conditions set from the base station. The report conditions maybe set to be reported periodically or at the time of occurrence of anevent according to the measurement values of the serving cell and theneighboring cells similarly to the LTE (4 h-60).

FIG. 4I is a block diagram illustrating an internal structure of theterminal to which the present disclosure is applied.

Referring to FIG. 4I, the terminal includes a radio frequency (RF)processor 4 i-10, a baseband processor 4 i-20, a memory 4 i-30, and acontroller 4 i-40.

The RF processor 4 i-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 4 i-10 up-converts a baseband signal providedfrom the baseband processor 4 i-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. Forexample, the RF processor 4 i-10 may include a transmitting filter, areceiving filter, an amplifier, a mixer, an oscillator, a digital toanalog converter (DAC), an analog to digital converter (ADC), or thelike. In the above figure, only one antenna is illustrated, but theterminal may include a plurality of antennas. Further, the RF processor4 i-10 may include a plurality of RF chains. Further, the RF processor 4i-10 may perform beamforming. For the beamforming, the RF processor 4i-10 may adjust a phase and a size of each of the signals transmittedand received through a plurality of antennas or antenna elements. Inaddition, the RF processor may perform MIMO and may receive a pluralityof layers when performing a MIMO operation.

The baseband processor 4 i-20 performs a conversion function between abaseband signal and a bit string according to a physical layer standardof a system. For example, when data are transmitted, the basebandprocessor 4 i-20 generates complex symbols by coding and modulating atransmitted bit string. Further, when data are received, the basebandprocessor 4 i-20 recovers the received bit string by demodulating anddecoding the baseband signal provided from the RF processor 4 i-10. Forexample, according to the orthogonal frequency division multiplexing(OFDM) scheme, when data are transmitted, the baseband processor 4 i-20generates the complex symbols by coding and modulating the transmittingbit string, maps the complex symbols to sub-carriers, and then performsan inverse fast Fourier transform (IFFT) operation and a cyclic prefix(CP) insertion to construct the OFDM symbols. Further, when data arereceived, the baseband processor 4 i-20 divides the baseband signalprovided from the RF processor 4 i-10 in an OFDM symbol unit andrecovers the signals mapped to the sub-carriers by a fast Fouriertransform (FFT) operation and then recovers the received bit string bythe modulation and decoding.

The baseband processor 4 i-20 and the RF processor 4 i-10 transmit andreceive a signal as described above. Therefore, the baseband processor 4i-20 and the RF processor 4 i-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. Further, at least oneof the baseband processor 4 i-20 and the RF processor 4 i-10 may includea plurality of communication modules to support a plurality of differentradio access technologies. Further, at least one of the basebandprocessor 4 i-20 and the RF processor 4 i-10 may include differentcommunication modules to process signals in different frequency bands.For example, different radio access technologies may include the WLAN(for example: IEEE 802.11), a cellular network (for example: LTE), orthe like. Further, the different frequency bands may include a superhigh frequency (SHF) (for example: 2 NRHz, NRhz) band, a millimeter wave(for example: 60 GHz) band.

The memory 4 i-30 stores data such as basic programs, applicationprograms, and configuration information for the operation of theterminal. In particular, the memory 4 i-30 may store informationassociated with a second access node performing wireless communicationusing a second access technology. Further, the memory 4 i-30 providesthe stored data according to the request of the controller 4 i-40.

The controller 4 i-40 controls the overall operations of the terminal.For example, the controller 4 i-40 transmits and receives a signalthrough the baseband processor 4 i-20 and the RF processor 4 i-10.Further, the controller 4 i-40 records and reads data in and from thememory 4 i-30. For this purpose, the controller 4 i-40 may include atleast one processor. For example, the controller 4 i-40 may include acommunication processor (CP) performing a control for communication andan application processor (AP) controlling an upper layer such as theapplication programs. According to the embodiment of the presentdisclosure, the controller 4 i-40 includes a multi-link processor 4 i-42that performs the processing to be operated in a multi-link mode.

FIG. 4J is a block diagram illustrating a configuration of the basestation according to the present disclosure.

As illustrated in FIG. 4J, the base station is configured to include anRF processor 4 j-10, a baseband processor 4 j-20, a backhaulcommunication unit 4 j-30, a memory 4 j-40, and a controller 4 j-50.

The RF processor 4 j-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 4 j-10 up-converts a baseband signal providedfrom the baseband processor 4 j-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. Forexample, the RF processor 4 j-10 may include a transmitting filter, areceiving filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,or the like. In the above figure, only one antenna is illustrated, butthe first access node may include a plurality of antennas. Further, theRF processor 4 j-10 may include a plurality of RF chains. Further, theRF processor 4 j-10 may perform the beamforming. For the beamforming,the RF processor 4 j-10 may adjust a phase and a size of each of thesignals transmitted/received through a plurality of antennas or antennaelements. The RF processor may perform a downward MIMO operation bytransmitting one or more layers.

The baseband processor 4 j-20 performs a conversion function between thebaseband signal and the bit string according to the physical layerstandard of the first radio access technology. For example, when dataare transmitted, the baseband processor 4 j-20 generates complex symbolsby coding and modulating a transmitted bit string. Further, when dataare received, the baseband processor 4 j-20 recovers the received bitstring by demodulating and decoding the baseband signal provided fromthe RF processor 4 j-10. For example, according to the OFDM scheme, whendata are transmitted, the baseband processor 4 j-20 generates thecomplex symbols by coding and modulating the transmitting bit string,maps the complex symbols to the sub-carriers, and then performs the IFFToperation and the CP insertion to construct the OFDM symbols. Further,when data are received, the baseband processor 4 j-20 divides thebaseband signal provided from the RF processor 4 j-10 in the OFDM symbolunit and recovers the signals mapped to the sub-carriers by the FFToperation and then recovers the receiving bit string by the modulationand decoding. The baseband processor 4 j-20 and the RF processor 4 j-10transmit and receive a signal as described above. Therefore, thebaseband processor 4 j-20 and the RF processor 4 j-10 may be called atransmitter, a receiver, a transceiver, or a communication unit.

The backhaul communication unit 4 j-30 provides an interface forperforming communication with other nodes within the network. That is,the backhaul communication unit 4 j-30 converts bit strings transmittedfrom the main base station to other nodes, for example, an auxiliarybase station, a core network, etc., into physical signals and convertsthe physical signals received from other nodes into the bit strings.

The memory 4 j-40 stores data such as basic programs, applicationprograms, and configuration information for the operation of the mainbase station. In particular, the memory 4 j-40 may store the informationon the bearer allocated to the accessed terminal, the measured resultsreported from the accessed terminal, etc. Further, the memory 4 j-40 maystore information that is a determination criterion on whether toprovide a multiple connection to the terminal or stop the multipleconnection to the terminal. Further, the memory 4 j-40 provides thestored data according to the request of the controller 4 j-50.

The controller 4 j-50 controls the general operations of the main basestation. For example, the controller 4 j-50 transmits/receives a signalthrough the baseband processor 4 j-20 and the RF processor 4 j-10 or thebackhaul communication unit 4 j-30. Further, the controller 4 j-50records and reads data in and from the memory 4 j-40. For this purpose,the controller 4 j-50 may include at least one processor. According tothe embodiment of the present disclosure, the controller 4 j-50 includesa multi-link processor 4 j-52 that performs the processing to beoperated in a multi-link mode.

FIG. 5A is a diagram illustrating a structure of the next generationmobile communication system.

Referring to FIG. 5A, a radio access network of a next generation mobilecommunication system is configured to include a next generation basestation (New radio node B, hereinafter NR NB or NR base station) 5 a-10and a new radio core network (NR CN) 5 a-05. The user terminal (newradio user equipment, hereinafter, NR UE or UE) 5 a-15 accesses theexternal network through the NR NB 5 a-10 and the NR CN 5 a-05.

In FIG. 5A, the NR NB 5 a-10 corresponds to an evolved node B (eNB) ofthe existing LTE system. The NR NB is connected to the NR UE 5 a-15 viaa radio channel and may provide a service superior to the existing nodeB. In the next generation mobile communication system, since all usertraffics are served through a shared channel, an apparatus forcollecting state information such as a buffer state, an availabletransmission power state, and a channel state of the UEs to performscheduling is used. The NR NB 5 a-10 may serve as the device. One NR NBgenerally controls a plurality of cells. In order to realize thehigh-speed data transmission compared with the existing LTE, the NR gNBmay have the existing maximum bandwidth or more, and may be additionallyincorporated into a beam-forming technology by using orthogonalfrequency division multiplexing (hereinafter, referred to as OFDM) as aradio access technology. Further, an adaptive modulation & coding(hereinafter, referred to as AMC) determining a modulation scheme and achannel coding rate according to a channel status of the terminal isapplied. The NR CN 5 a-05 may perform functions such as mobilitysupport, bearer setup, QoS setup, and the like. The NR CN is anapparatus for performing a mobility management function for the terminaland various control functions and is connected to a plurality of basestations. In addition, the next generation mobile communication systemcan interwork with the existing LTE system, and the NR CN is connectedto the MME 5 a-25 through the network interface. The MME is connected tothe eNB 5 a-30 which is the existing base station.

FIG. 5B is a diagram illustrating a case in which an access connectionconfiguration information is urgently renewed in the existing LTEsystem.

In the LTE system, when there is system information to be updated, thesystem information is informed to the terminal informs using a pagingmessage. The paging information is updated or immediately updatedaccording to the type of system information to be updated when beingreceived. Except for specific system information such as ETWS/CMAS andextended access barring (EAB), for most system information, the updatetime is determined based on the modification period. The ModificationPeriod is the time period set by the network. The boundary of theModification Period is the time when SFN mod m=0. Here, m is the timeperiod of the Modification Period and is set by the network. If thenetwork provides the updated system information in the n-th ModificationPeriod, the network uses the paging message in the n−1-th Modificationto inform the terminal that the updated system information is providedform the Modification Period. The EAB which is the access connectionconfiguration information of the ETWS/CMAS or the mechanicalcommunication device for the purpose of disaster alarm needs to beprovided to a terminal 5 b-15 as soon as possible when a disaster occurs(5 b-15) or a network congestion (5 b-45) occurs. The ETWS/CMASconfiguration information indicates that a disaster situation hasoccurred and may include relevant information together. The EAB is oneof the access connection configuration information, and is informationnecessary for determining whether the mechanical communication devicesmay access the network. If the configuration information is updatedbased on the Modification Period, a delay occurs until the nextModification Period. Therefore, when the terminal receives the pagingmessage including the separate indicator 5 b-20 from the base station 5b-10, it immediately updates the configuration information regardless ofthe Modification Period (5 b-25, 5 b-55). The ETWS/CMAS configurationinformation is provided to the SIB 10, the SIB 11, and the SIB 12, andit is necessary to first receive the SIB 1 including the schedulinginformation of the system information in order to receive it. Theterminal receiving the paging message including the separate indicatorimmediately receives the SIB1 (5 b-30), and then receives the SIB10,SIB11, and SIB12 (5 b-35). The EAB configuration information is includedin the SIB 14, and the terminal receiving the paging message includingthe separate indicator 5 b-50 immediately receives the SIB1 (5 b-60) andthen receives the SIB14 (5 b-65). The terminal that has obtained theconfiguration information immediately applies it (5 b-40, 5 b-70).

FIG. 5C is a diagram illustrating a method for renewing accessconnection configuration information in the next generation mobilecommunication system according to the present disclosure.

In the next generation mobile communication system, the accessconnection configuration information will be provided based on thecategory. One category is mapped to the following various elements.

-   -   Application triggering the access    -   Services (e.g. MMTEL voice, MMTEL video, SMS)    -   Call types (e.g. emergency access, high priority access, MT        access)    -   Device/subscription indicators (e.g. low priority UEs)    -   Signaling procedure(s) (e.g. NAS procedures, RRC procedures)    -   Slice

For example, an emergency call may be mapped to category 0,highPriorityAccess call may be mapped to Category 1, EAB call may bemapped to Category 5, and Application 1 call may be mapped to Category12.

The network provides the access connection configuration informationcorresponding to each category as the system information. Afteridentifying which category the access triggered by the terminalcorresponds to, the terminal uses the corresponding access connectionconfiguration information to determine whether or not the access ispermitted. The access connection configuration information for eachcategory may be included in another SIB according to the same SIB orcategory. The present disclosure is characterized in that the accessconnection configuration information to be immediately updated andapplied is indicated on a category basis. When the network 5 c-10recognizes the network congestion state (5 c-15), it updates the accessconnection configuration information corresponding to the category inorder to suppress the access belonging to the specific category and thenprovides the updated access connection setting information to theterminals within the service region as the system information. Inaddition, it indicates to the terminals in the service area by thepaging message 5 c-20 whether the access connection configurationinformation belonging to which category should be immediately updatedand applied. The terminal receiving the paging message immediatelyreceives the access configuration information corresponding to theindicated category (5 c-25). The access configuration information willbe included in the Minimum SI (system information). The Minimum SIincludes essential system information. It includes informationcorresponding to MIB, SIB1, and SIB2 in the LTE system. The Minimum SIis periodically broadcast. All contents of the Minimum SI may beprovided to the NR-PBCH channel (5 c-30), some of the contents may beprovided to the NR-PBCH (5 c-35), and the remaining contents may beprovided to the terminal using another channel. When only some of thecontents are transmitted to the NR-PBCH, the NR-PBCH includes schedulinginformation necessary for receiving the content of the remaining MinimumSI. The access connection configuration information may be included inthe Minimum SI transmitted to the NR-PBCH or another channel. The accessconnection configuration information for the ETWS/CAMS, or mechanicalcommunication device may be included in the NR-PBCH. This is because thetime required for the terminal to update and apply it can be somewhatreduced. The terminal receiving the access connection configurationinformation corresponding to the category indicated by the pagingmessage immediately applies the configuration information (5 c-45). Theaccess connection configuration information corresponding to thecategory may be included in the same SIB. Accordingly, the terminal mayimmediately receive the SIB and acquire the access connectionconfiguration information corresponding to the category that is notimmediately updated. However, the access connection configurationinformation that is actually applied immediately is the accessconnection configuration information corresponding to the categoryindicated in the paging message.

In another embodiment, the SIB information to be updated immediately maybe included. For example, the network can perform the indication usingthe paging message to immediately update SIB4, SIB10, and SIB14. Thepaging message includes an indicator indicating SIB4, SIB10, and SIB14.Upon receiving the indicator, the terminal immediately starts the SIBreception operation. In addition, although not indicated in the pagingmessage, the terminal needs to receive an SIB including schedulinginformation of other SIBs.

FIG. 5D illustrates a flowchart of the terminal operation in the presentdisclosure.

In step 5 d-05, the terminal receives the paging message from thenetwork. In step 5 d-10, the terminal confirms that the received pagingmessage has an indicator indicating that there is an access connectionsetting information to be immediately updated. The indicator is categoryinformation corresponding to the access connection setting information.For example, the information is a category ID. Alternatively, the SIBinformation to be immediately updated may be included in the pagingmessage. The category information or the SIB information may be providedin a bitmap form. In step 5 d-15, the terminal receives the SIBincluding access connection configuration information corresponding tothe category. In step 5 d-20, the terminal applies the updated accessconnection configuration information.

FIG. 5E is a diagram illustrating a first method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure.

The category information stored in the paging message may be indicatedin bitmap form. The size of the bitmap corresponds to the total numberof categories provided by the network. Each bit stored in the bitmapcorresponds to one category (5 e-25), and the order is the same as thecategory ID order or the category list order. There is one bitmap foreach PLMN 5 e-05, 5 e-10, 5 e-15, and 5 e-20. This is because differentcategories and the corresponding access connection configurationinformation may be provided to each PLMN. Thus, the sizes of the bitmapsfor each PLMN may be different.

FIG. 5F is a diagram illustrating a second method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure.

The system information related to the disaster alarm may be indicated inbitmap form included in the paging message (5 f-05). Each bitcorresponds to one disaster alarm.

The system information to be updated and applied immediately may beindicated for each SIB. The SIB information stored in the paging messagemay be indicated in bitmap form. The size of the bitmap corresponds tothe total number of SIBs provided by the network. Each bit stored in thebitmap corresponds to one SIB (5 f-10), and the order thereof is thesame as that of the SIB in the network.

FIG. 5G is a diagram illustrating a third method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure.

It is possible to immediately update and apply the access connectionconfiguration information corresponding to all categories. Since thebitmap form requires a large number of bits, if a 1-bit indicatorindicating a specific case is defined as described above, unnecessarysignaling overhead may be reduced. The 1-bit indicator or the 1-bitindicator (5 g-10) for each PLMN is used to indicate that the accessconnection configuration information corresponding to all categories orthe access connection configuration information corresponding to allcategories belonging to one PLMN is immediately updated and applied. Theindicator is stored in the paging message, and when the indicator isset, the bitmap information is ignored even if the bitmap information (5g-15) is included in the paging message.

FIG. 5H is a diagram illustrating a fourth method for renewing accessconnection configuration information to be urgently renewed in thepresent disclosure.

Only the terminals belonging to a specific group can apply the accessconnection configuration information. To this end, the indicatorindicating the specific group is included in the paging message. Theindicator may be the bitmap form, or an ENUMERATED form. For example,they may be classified into three groups as follows.

Group A

-   -   corresponds to all UEs Group B    -   corresponds to the UEs that are neither in their HPLMN nor in a        PLMN that is equivalent to it

Group C

-   -   corresponds to the UEs that are neither in the PLMN listed as        most preferred PLMN of the country where the UEs are roaming in        the operator-defined PLMN selector list on the USIM, nor in        their HPLMN nor in a PLMN that is equivalent to their HPLMN

The groups may be provided for each category or common to allcategories. If the information is not provided, the terminal isconsidered the group A. For example, category 1 is set as the accessconnection setting information to be immediately updated in the pagingmessage. If the group B is indicated with respect to the category, theterminal identifies whether it belongs to the group B, and if theterminal belongs to the group B, The access connection configurationinformation corresponding the category 1 is immediately updated andapplied.

The structure of the terminal is illustrated in FIG. 5I.

Referring to FIG. 5I, the terminal includes a radio frequency (RF)processor 5 i-10, a baseband processor 5 i-20, a memory 5 i-30, and acontroller 5 i-40.

The RF processor 5 i-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 5 i-10 up-converts a baseband signal providedfrom the baseband processor 5 i-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. Forexample, the RF processor 5 i-10 may include a transmitting filter, areceiving filter, an amplifier, a mixer, an oscillator, a digital toanalog converter (DAC), an analog to digital converter (ADC), or thelike. In the above figure, only one antenna is illustrated, but theterminal may include a plurality of antennas. Further, the RF processor5 i-10 may include a plurality of RF chains. Further, the RF processor 5i-10 may perform beamforming. For the beamforming, the RF processor 5i-10 may adjust a phase and a size of each of the signals transmittedand received through a plurality of antennas or antenna elements. Inaddition, the RF processor may perform MIMO and may receive a pluralityof layers when performing a MIMO operation.

The baseband processor 5 i-20 performs a conversion function between abaseband signal and a bit string according to a physical layer standardof a system. For example, when data are transmitted, the basebandprocessor 5 i-20 generates complex symbols by coding and modulating atransmitted bit string. Further, when data are received, the basebandprocessor 5 i-20 recovers the received bit string by demodulating anddecoding the baseband signal provided from the RF processor 5 i-10. Forexample, according to the orthogonal frequency division multiplexing(OFDM) scheme, when data are transmitted, the baseband processor 5 i-20generates the complex symbols by coding and modulating the transmittingbit string, maps the complex symbols to sub-carriers, and then performsan inverse fast Fourier transform (IFFT) operation and a cyclic prefix(CP) insertion to construct the OFDM symbols. Further, when data arereceived, the baseband processor 5 i-20 divides the baseband signalprovided from the RF processor 5 i-10 in an OFDM symbol unit andrecovers the signals mapped to the sub-carriers by a fast Fouriertransform (FFT) operation and then recovers the received bit string bythe modulation and decoding.

The baseband processor 5 i-20 and the RF processor 5 i-10 transmit andreceive a signal as described above. Therefore, the baseband processor 5i-20 and the RF processor 5 i-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. Further, at least oneof the baseband processor 5 i-20 and the RF processor 5 i-10 may includea plurality of communication modules to support a plurality of differentradio access technologies. Further, at least one of the basebandprocessor 5 i-20 and the RF processor 5 i-10 may include differentcommunication modules to process signals in different frequency bands.For example, different radio access technologies may include the WLAN(for example: IEEE 802.11), a cellular network (for example: LTE), orthe like. Further, the different frequency bands may include a superhigh frequency (SHF) (for example: 2 NRHz, NRhz) band, a millimeter wave(for example: 60 GHz) band.

The memory 5 i-30 stores data such as basic programs, applicationprograms, and configuration information for the operation of theterminal. In particular, the memory 5 i-30 may store informationassociated with a second access node performing wireless communicationusing a second access technology. Further, the memory 5 i-30 providesthe stored data according to the request of the controller 5 i-40.

The controller 5 i-40 controls the overall operations of the terminal.For example, the controller 5 i-40 transmits and receives a signalthrough the baseband processor 5 i-20 and the RF processor 5 i-10.Further, the controller 5 i-50 records and reads data in and from thememory 5 i-30. For this purpose, the controller 5 i-40 may include atleast one processor. For example, the controller 5 i-40 may include acommunication processor (CP) performing a control for communication andan application processor (AP) controlling an upper layer such as theapplication programs. According to the embodiment of the presentdisclosure, the controller 5 i-40 includes a multi-link processor 5 i-42that performs the processing to be operated in a multi-link mode.

FIG. 5J illustrates a block configuration diagram of a main base stationin a wireless communication system according to an embodiment of thepresent disclosure.

As illustrated in FIG. 5J, the base station is configured to include anRF processor 5 j-10, a baseband processor 5 j-20, a backhaulcommunication unit 5 j-30, a memory 5 j-40, and a controller 5 j-50.

The RF processor 5 j-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 5 j-10 up-converts a baseband signal providedfrom the baseband processor 5 j-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. Forexample, the RF processor 5 j-10 may include a transmitting filter, areceiving filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,or the like. In the above figure, only one antenna is illustrated, butthe first access node may include a plurality of antennas. Further, theRF processor 5 j-10 may include a plurality of RF chains. Further, theRF processor 5 j-10 may perform the beamforming. For the beamforming,the RF processor 5 j-10 may adjust a phase and a size of each of thesignals transmitted/received through a plurality of antennas or antennaelements. The RF processor may perform a downward MIMO operation bytransmitting one or more layers.

The baseband processor 5 j-20 performs a conversion function between thebaseband signal and the bit string according to the physical layerstandard of the first radio access technology. For example, when dataare transmitted, the baseband processor 5 j-20 generates complex symbolsby coding and modulating a transmitted bit string. Further, when dataare received, the baseband processor 5 j-20 recovers the received bitstring by demodulating and decoding the baseband signal provided fromthe RF processor 5 j-10. For example, according to the OFDM scheme, whendata are transmitted, the baseband processor 5 j-20 generates thecomplex symbols by coding and modulating the transmitting bit string,maps the complex symbols to the sub-carriers, and then performs the IFFToperation and the CP insertion to construct the OFDM symbols. Further,when data are received, the baseband processor 5 j-20 divides thebaseband signal provided from the RF processor 5 j-10 in the OFDM symbolunit and recovers the signals mapped to the sub-carriers by the FFToperation and then recovers the receiving bit string by the modulationand decoding. The baseband processor 5 j-20 and the RF processor 5 j-10transmit and receive a signal as described above. Therefore, thebaseband processor 5 j-20 and the RF processor 5 j-10 may be called atransmitter, a receiver, a transceiver, or a communication unit.

The backhaul communication unit 5 j-30 provides an interface forperforming communication with other nodes within the network. That is,the backhaul communication unit 5 j-30 converts bit strings transmittedfrom the main base station to other nodes, for example, an auxiliarybase station, a core network, etc., into physical signals and convertsthe physical signals received from other nodes into the bit strings.

The memory 5 j-40 stores data such as basic programs, applicationprograms, and configuration information for the operation of the mainbase station. In particular, the memory 5 j-40 may store the informationon the bearer allocated to the accessed terminal, the measured resultsreported from the accessed terminal, etc. Further, the memory 5 j-40 maystore information that is a determination criterion on whether toprovide a multiple connection to the terminal or stop the multipleconnection to the terminal. Further, the memory 5 j-40 provides thestored data according to the request of the controller 5 j-50.

The controller 5 j-50 controls the general operations of the main basestation. For example, the controller 5 j-50 transmits/receives a signalthrough the baseband processor 5 j-20 and the RF processor 5 j-10 or thebackhaul communication unit 5 j-30. Further, the controller 5 j-50records and reads data in and from the memory 5 j-40. For this purpose,the controller 5 j-50 may include at least one processor. According tothe embodiment of the present disclosure, the controller 5 j-50 includesa multi-link processor 5 j-52 that performs the processing to beoperated in a multi-link mode.

Although the present disclosure has been described with variousembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method performed by a receiving apparatus in awireless communication system, the method comprising: receiving, from atransmitting apparatus, a radio link control (RLC) protocol data unit(PDU); generating a status PDU based on the RLC PDU; and transmittingthe status PDU to the transmitting apparatus, wherein the status PDUincludes an extension bit 1 (E1) field indicating whether a negativeacknowledgement sequence number (NACK_SN) field, an E1 field, anextension bit 2 (E2) field and an extension bit 3 (E3) field follow,wherein the NACK_SN field includes a first sequence number (SN) of anRLC data unit identified as lost, the E2 field indicates whether asegment offset (SO) start field and an SO end field follow, the E3 fieldindicates whether a NACK_range field follows, and the NACK_range fieldincludes a number of consecutively lost RLC data units starting from andincluding the first SN, and wherein a first reserved (R) field is placedimmediately after the E1 field and an octet including the first R fieldis byte aligned based on the first R field.
 2. The method of claim 1,wherein a second R field is placed immediately after the E3 field and anoctet including the second R field is byte aligned based on the second Rfield.
 3. The method of claim 1, wherein the SO start field indicates aposition of a first byte of a portion of the RLC data unit associatedwith the first SN in bytes, and wherein the SO end field indicates aposition of a last byte of a portion of an RLC data unit associated witha second SN identified based on the NACK range field in bytes, in casethat the E3 field indicates that the NACK_range field follows for theNACK_SN field.
 4. The method of claim 3, wherein the second SN isidentified based on the NACK_range field by setting the second SN equalto the first SN indicated by the NACK SN field plus the number ofconsecutively lost RLC data units indicated by the NACK_range field −1.5. A method performed by a transmitting apparatus in a wirelesscommunication system, the method comprising: transmitting, to areceiving apparatus, a radio link control (RLC) protocol data unit(PDU); and receiving, from the receiving apparatus, a status PDUgenerated based on the RLC PDU, wherein the status PDU includes anextension bit 1 (E1) field indicating whether a negative acknowledgementsequence number (NACK_SN) field, an E1 field, an extension bit 2 (E2)field and an extension bit 3 (E3) field follow, wherein the NACK_SNfield includes a first sequence number (SN) of an RLC data unitidentified as lost, the E2 field indicates whether a segment offset (SO)start field and an SO end field follow, the E3 field indicates whether aNACK_range field follows, and the NACK_range field includes a number ofconsecutively lost RLC data units starting from and including the firstSN, and wherein a first reserved (R) field is placed immediately afterthe E1 field and an octet including the first R field is byte alignedbased on the first R field.
 6. The method of claim 5, wherein a second Rfield is placed immediately after the E3 field and an octet includingthe second R field is byte aligned based on the second R field.
 7. Themethod of claim 5, wherein the SO start field indicates a position of afirst byte of a portion of the RLC data unit associated with the firstSN in bytes, and wherein the SO end field indicates a position of a lastbyte of a portion of an RLC data unit associated with a second SNidentified based on the NACK range field in bytes, in case that the E3field indicates that the NACK_range field follows for the NACK_SN field.8. The method of claim 7, wherein the second SN is identified based onthe NACK_range field by setting the second SN equal to the first SNindicated by the NACK SN field plus the number of consecutively lost RLCdata units indicated by the NACK_range field −1.
 9. A receivingapparatus in a wireless communication system, the receiving apparatuscomprising: a transceiver; and a controller configured to: receive, froma transmitting apparatus via the transceiver, a radio link control (RLC)protocol data unit (PDU), generate a status PDU based on the RLC PDU,and transmit the status PDU to the transmitting apparatus via thetransceiver, wherein the status PDU includes an extension bit 1 (E1)field indicating whether a negative acknowledgement sequence number(NACK_SN) field, an E1 field, an extension bit 2 (E2) field and anextension bit 3 (E3) field follow, wherein the NACK_SN field includes afirst sequence number (SN) of an RLC data unit identified as lost, theE2 field indicates whether a segment offset (SO) start field and an SOend field follow, the E3 field indicates whether a NACK_range fieldfollows, and the NACK_range field includes a number of consecutivelylost RLC data units starting from and including the first SN, andwherein a first reserved (R) field is placed immediately after the E1field and an octet including the first R field is byte aligned based onthe first R field.
 10. The receiving apparatus of claim 9, wherein asecond R field is placed immediately after the E3 field and an octetincluding the second R field is byte aligned based on the second Rfield.
 11. The receiving apparatus of claim 9, wherein the SO startfield indicates a position of a first byte of a portion of the RLC dataunit associated with the first SN in bytes, and wherein the SO end fieldindicates a position of a last byte of a portion of an RLC data unitassociated with a second SN identified based on the NACK range field inbytes, in case that the E3 field indicates that the NACK_range fieldfollows for the NACK_SN field.
 12. The receiving apparatus of claim 11,wherein the second SN is identified based on the NACK_range field bysetting the second SN equal to the first SN indicated by the NACK_SNfield plus the number of consecutively lost RLC data units indicated bythe NACK_range field −1.
 13. A transmitting apparatus in a wirelesscommunication system, the transmitting apparatus comprising: atransceiver; and a controller configured to: transmit, to a receivingapparatus via the transceiver, a radio link control (RLC) protocol dataunit (PDU), and receive, from the receiving apparatus via thetransceiver, a status PDU generated based on the RLC PDU, wherein thestatus PDU includes an extension bit 1 (E1) field indicating whether anegative acknowledgement sequence number (NACK_SN) field, an E1 field,an extension bit 2 (E2) field and an extension bit 3 (E3) field follow,wherein the NACK_SN field includes a first sequence number (SN) of anRLC data unit identified as lost, the E2 field indicates whether asegment offset (SO) start field and an SO end field follow, the E3 fieldindicates whether a NACK_range field follows, and the NACK_range fieldincludes a number of consecutively lost RLC data units starting from andincluding the first SN, and wherein a first reserved (R) field is placedimmediately after the E1 field and an octet including the first R fieldis byte aligned based on the first R field.
 14. The transmittingapparatus of claim 13, wherein a second R field is placed immediatelyafter the E3 field and an octet including the second R field is bytealigned based on the second R field.
 15. The transmitting apparatus ofclaim 13, wherein the SO start field indicates a position of a firstbyte of a portion of the RLC data unit associated with the first SN inbytes, and wherein the SO end field indicates a position of a last byteof a portion of an RLC data unit associated with a second SN identifiedbased on the NACK_range field in bytes, in case that the E3 fieldindicates that the NACK_range field follows for the NACK_SN field. 16.The transmitting apparatus of claim 15, wherein the second SN isidentified based on the NACK_range field by setting the second SN equalto the first SN indicated by the NACK SN field plus the number ofconsecutively lost RLC data units indicated by the NACK_range field −1.